USA Toll Transponder Interoperability - 2026 edition

[I-55]

BREAKING NEWS: PikePass has announced that E-ZPass is now accepted on their system!
The following states now accept PikePass from the E-ZPass hub- IL (Illinois Tollway system and Chicago Skyway), IN (Indiana Toll Road), MA, NC, PA (Pennsylvania Turnpike Commission)

https://pikepass.com/plan-your-trip/interoperability

I'm a little confused. I clicked the link but it basically says you can now use PikePass in the additional states you listed, but it said nothing about actually being able to use E-ZPass on the OTA roads, and the E-ZPass website itself still doesn't mention OK. Am I missing something?

I imagine the E-ZPass site won't be updated until all E-ZPass member agencies are interoperable. Remember, the integration of the Central Hub into the E-ZPass hub is being performed in phases, with IL, IN, PA, NC being the first wave. I haven't seen anything on those states' pages regarding Pikepass interoperability, though KTA's page is now displaying "New" interoperability with select E-ZPass states. I'm still awaiting official word from the Illinois Tollway that my I-Pass works in the Central Hub States.

[kphoger]

I imagine the E-ZPass site won't be updated until all E-ZPass member agencies are interoperable. Remember, the integration of the Central Hub into the E-ZPass hub is being performed in phases, with IL, IN, PA, NC being the first wave. I haven't seen anything on those states' pages regarding Pikepass interoperability, though KTA's page is now displaying "New" interoperability with select E-ZPass states. I'm still awaiting official word from the Illinois Tollway that my I-Pass works in the Central Hub States.

Well, there is this:

https://driveks.com/help/faq?id=3

What electronic transponders are accepted on Kansas toll facilities?

The following transponders are currently accepted on Kansas toll facilities: KTAG (Kansas); BestPass (multiple states); Pikepass (Oklahoma); PrePass Plus (multiple states); EZ TAG (Texas); TxTag (Texas); TollTag (Texas); ExpressToll (Colorado); SunPass - Pro and Mini (Florida); BancPass (multiple states), NationalPass (multiple states) and E-ZPass (multiple states).

And you can always call customer service:
1-800-873-5824
Monday - Friday, 7:30 am - 6:30 pm

[ElishaGOtis]

I imagine the E-ZPass site won't be updated until all E-ZPass member agencies are interoperable. Remember, the integration of the Central Hub into the E-ZPass hub is being performed in phases, with IL, IN, PA, NC being the first wave. I haven't seen anything on those states' pages regarding Pikepass interoperability, though KTA's page is now displaying "New" interoperability with select E-ZPass states. I'm still awaiting official word from the Illinois Tollway that my I-Pass works in the Central Hub States.

Well, there is this:

https://driveks.com/help/faq?id=3

What electronic transponders are accepted on Kansas toll facilities?

The following transponders are currently accepted on Kansas toll facilities: KTAG (Kansas); BestPass (multiple states); Pikepass (Oklahoma); PrePass Plus (multiple states); EZ TAG (Texas); TxTag (Texas); TollTag (Texas); ExpressToll (Colorado); SunPass - Pro and Mini (Florida); BancPass (multiple states), NationalPass (multiple states) and E-ZPass (multiple states).

And you can always call customer service:
1-800-873-5824
Monday - Friday, 7:30 am - 6:30 pm

Did exactly that. E-ZPass from IL, IN, PA, MA, and NC work in Kansas and K-Tag works in those specific states, per phone call.

Still a SunPass Pro fan though 

[ElishaGOtis]

ExpressToll also now extends to those states.

https://www.expresstoll.com/travel-info/interoperability

[ElishaGOtis]

Confirmed by phone call that NTTA has not yet joined.

[Great Lakes Roads]

Confirmed by phone call that NTTA has not yet joined.

https://www.ntta.org/plan-your-trip

Can confirm that NTTA now accepts E-ZPass.

[ElishaGOtis]

Can confirm E-ZPass Flex and ExpressToll+ are not yet interoperable for HOV discounts per phone calls with NC & CO.

[Thing 342]

Got an e-mail today announcing that NC Quick Pass is now accepted at K-Tag, PikePass, NTTA, and E-470 readers: https://www.ncquickpass.com/where-nc-quick-pass-works/

[SSOWorld]

New PDF uploaded to original post

This reflects both the recent confirmed reports by E-470 Public Highway Authority (Colorado), Kansas Turnpike Authority (KTA), Oklahoma Turnpike Authority (OTA), North Texas Turnpike Authority (NTTA), and North Carolina Turnpike Authority (NCTA).  All other rumored E-Z Pass/Central Hub have NOT been marked as Y yet - which will not be done until first-source confirmation. Please keep the updates coming - I will have to check personally before I update.

While KTA has mentioned that the confirmed E-Z Pass agencies should work on Kansas Toll roads, I am not reflecting that in the document yet.

On that note - while (if) I am able to use I-PASS in KS, OK and on the NTTA roads, - I will still need my KTAG for the rest of Texas.

Note that in Indiana - only the Indiana Toll Road is supported, and in PA, only the PA Turnpike Commission toll roads are supported.  Only E-470 has announced interoperability with OH-TPK and MDTA.

[Great Lakes Roads]

New PDF uploaded to original post

This reflects both the recent confirmed reports by E-470 Public Highway Authority (Colorado), Kansas Turnpike Authority (KTA), Oklahoma Turnpike Authority (OTA), North Texas Turnpike Authority (NTTA), and North Carolina Turnpike Authority (NCTA).  All other rumored E-Z Pass/Central Hub have NOT been marked as Y yet - which will not be done until first-source confirmation. Please keep the updates coming - I will have to check personally before I update.

While KTA has mentioned that the confirmed E-Z Pass agencies should work on Kansas Toll roads, I am not reflecting that in the document yet.

On that note - while (if) I am able to use I-PASS in KS, OK and on the NTTA roads, - I will still need my KTAG for the rest of Texas.

Note that in Indiana - only the Indiana Toll Road is supported, and in PA, only the PA Turnpike Commission toll roads are supported.  Only E-470 has announced interoperability with OH-TPK and MDTA.

Can confirm from my dad that the PikePass sticker works on both the Chicago Skyway and the Indiana Toll Road (and it's a lot faster to respond than the E-ZPass transponder).

[I-55]

New PDF uploaded to original post

This reflects both the recent confirmed reports by E-470 Public Highway Authority (Colorado), Kansas Turnpike Authority (KTA), Oklahoma Turnpike Authority (OTA), North Texas Turnpike Authority (NTTA), and North Carolina Turnpike Authority (NCTA).  All other rumored E-Z Pass/Central Hub have NOT been marked as Y yet - which will not be done until first-source confirmation. Please keep the updates coming - I will have to check personally before I update.

While KTA has mentioned that the confirmed E-Z Pass agencies should work on Kansas Toll roads, I am not reflecting that in the document yet.

On that note - while (if) I am able to use I-PASS in KS, OK and on the NTTA roads, - I will still need my KTAG for the rest of Texas.

Note that in Indiana - only the Indiana Toll Road is supported, and in PA, only the PA Turnpike Commission toll roads are supported.  Only E-470 has announced interoperability with OH-TPK and MDTA.

Can confirm from my dad that the PikePass sticker works on both the Chicago Skyway and the Indiana Toll Road (and it's a lot faster to respond than the E-ZPass transponder).

Illinois Tollway has updated their I-Pass page to include the Central Hub (though the map is still just the E-ZPass states)

Use your I-PASS on a growing national network of connected roads.

Traveling with I-PASS is easier now that it is accepted by toll facilities in 24 states across the country including E-ZPass facilities to the east and new partners in the Central United States.

https://agency.illinoistollway.com/about-ipass?_gl=1*1e7dhi*_ga*MzAzMDAyNjAzLjE3ODg0NTcwMzU.*_ga_M8DZPEZVK4*czE3ODg0NTcwMzQkbzEkZzEkdDE3ODg0NTcwMzckajU3JGwwJGgw

[SSOWorld]

New PDF uploaded to original post

This reflects both the recent confirmed reports by E-470 Public Highway Authority (Colorado), Kansas Turnpike Authority (KTA), Oklahoma Turnpike Authority (OTA), North Texas Turnpike Authority (NTTA), and North Carolina Turnpike Authority (NCTA).  All other rumored E-Z Pass/Central Hub have NOT been marked as Y yet - which will not be done until first-source confirmation. Please keep the updates coming - I will have to check personally before I update.

While KTA has mentioned that the confirmed E-Z Pass agencies should work on Kansas Toll roads, I am not reflecting that in the document yet.

On that note - while (if) I am able to use I-PASS in KS, OK and on the NTTA roads, - I will still need my KTAG for the rest of Texas.

Note that in Indiana - only the Indiana Toll Road is supported, and in PA, only the PA Turnpike Commission toll roads are supported.  Only E-470 has announced interoperability with OH-TPK and MDTA.

Can confirm from my dad that the PikePass sticker works on both the Chicago Skyway and the Indiana Toll Road (and it's a lot faster to respond than the E-ZPass transponder).

Illinois Tollway has updated their I-Pass page to include the Central Hub (though the map is still just the E-ZPass states)

Use your I-PASS on a growing national network of connected roads.

Traveling with I-PASS is easier now that it is accepted by toll facilities in 24 states across the country including E-ZPass facilities to the east and new partners in the Central United States.

https://agency.illinoistollway.com/about-ipass?_gl=1*1e7dhi*_ga*MzAzMDAyNjAzLjE3ODg0NTcwMzU.*_ga_M8DZPEZVK4*czE3ODg0NTcwMzQkbzEkZzEkdDE3ODg0NTcwMzckajU3JGwwJGgw

too vague. ISTHA needs datails.

[SSOWorld]

Intentional Double post

Agencies will not update their information right away. Many take quite a bit of time (months or more) to do so.  CRM and HCTRA are notorious for being stubborn to accept other passes (having put off acceptance of SunPass and ExpressToll for at least a year each)

Here is what each agency is saying regarding the new interoperability between Central US and E-Z Pass network equipment at the time of this post.

E470 - https://www.expresstoll.com/travel-info/interoperability
ExpressToll site explicitly indicates it is operable with the following E-Z pass agencies: MDTA (Maryland), and Ohio Turnpike and Infrastructure Commission, Pennsylvania Turnpike Authority, IN Toll Road Concession, Skyway Concession, ISTHA, NC Quick Pass, MassDOT. NOTE: Northwest Parkway's primary program is GO-PASS. They do accept ExpressToll transponders - but no other transponders (including KTAG, PikePass, TollTag and EZTag.)

KTA - This PDF indicates all of the agencies KTA has set up interoperability with.  The list is accessible through the DriveKS FAQ.  The E-Z Pass agency tags will work on all Kansas toll facilities. Updated 9/28 to include OTIC and MDTA.

PikePass - https://pikepass.com/plan-your-trip/interoperability Shows IL, IN, PA, MD, MA, OH, NC and lists the same agencies KTA did. The E-Z Pass agency tags will work on all OK Turnpikes

NTTA - https://www.ntta.org/plan-your-trip - Scroll down and select "New - PA, IL MA, NC, IN"

Customers regularly tell us they highly value the expanded travel options and convenience their TollTag provides.

Now, TollTag customers can use toll roads in Pennsylvania, Illinois, Massachusetts, North Carolina, and some toll roads in Indiana and receive the lowest toll rate.

WHERE TOLLTAG IS NOW ACCEPTED
•    Pennsylvania Turnpike Commission
•    Illinois State Highway Authority, Skyway Concession Company in Chicago
•    Massachusetts Department of Transportation
•    North Carolina Turnpike Authority
•    Indiana Toll Road Concession Company
•    Maryland Transportation Authority
•    Ohio Turnpike and Infrastructure Commission


NTTA customers using participating toll roads will have tolls automatically deducted from their TollTag account and posted to their monthly statement.

To take advantage of this convenience, drivers must have a TollTag account in good standing.

Vehicles should NOT have both a TollTag and transponders from another state. Please choose which toll account you would like to keep, close the other account and remove that sticker from your windshield.

The E-Z Pass agency tags will work on all NTTA roads. They will not work on other toll roads or any HOT lanes (Central Region Mobility, HCTRA, FBCTRA, TexPress, etc.)

Central Region Mobility (TX) - Does not list E-Z Pass, NC Quick Pass, or I-Pass as an accepted tag.

HCTRA - https://www.hctra.org/FAQ/Interoperability Their FAQ only indicates Florida, Oklahoma, Kansas and Colorado as of 7/22/2025.  Please note that TxTag is phasing out in favor of EZTag.

ISTHA- https://agency.illinoistollway.com/about-ipass

Traveling with I-PASS is easier now that it is accepted by toll facilities in 24 states across the country including E-ZPass facilities to the east and new partners in the Central United States.

However, the agency is not specifically stating which other Central US agencies are participating.  And how did they indicate 24 states?  Keep in mind Bay City, Michigan! KTAG, TollTag, PikePass and ExpressToll will work on all ISTHA roads (88, 90, the Tri-State, 355)

Chicago Skyway- https://www.chicagoskyway.org/toll-information/#ez-pass-info
The SCC relies E-Z Pass IAG to indicate interoperability and has not mentioned CUSIOP on their own site. KTAG, TollTag, PikePass and ExpressToll will work on the Skyway

Indiana Toll Road - https://www.indianatollroad.org/e-zpass/
ITRCC has not mentioned CUSIOP on their site KTAG, TollTag, PikePass and ExpressToll will work on the Indiana Toll Road. They will not work on the Cline Ave Bridge or the bridges to Kentucky.

MDTA - https://driveezmd.com/acct-types/e-zpass-regional-network/

Their site is extremely outdated - no show for Michigan or Minnesota much less CUSIOP.  If the information is accurate. Central Hub (sans EZTag) will work with all toll facilities in MD.

MassDOT - https://www.ezdrivema.com/AboutEZDriveMA

Does not mention ANY interoperability on the site.  KTAG, TollTag, PikePass and ExpressToll will work on the Mass Pike, Tobin Bridge, Sumner/Callahan Tunnels, and Ted Williams Tunnel

NC DOT (NC Turnpike Authority) - https://ncquickpass.com
if you have JavaScript enabled - you'll get an alert overlay with the following:

NC Quick Pass now works in 23 states. See how far your transponder can take you: view coverage.

They're not counting Michigan!!! KTAG, TollTag, PikePass and ExpressToll will work on all NC HoT Lanes

Ohio Turnpike - https://www.ohioturnpike.org/
https://www.ohioturnpike.org/ has confirmed interoperability with central hub but like ISTHA has not specified only NTTA for Texas.

Penna Turnpike - https://www.paturnpike.com/e-zpass

PTC relies on the E-Z Pass IAG to indicate interoperability and has not mentioned CUSIOP on their own site.  KTAG, TollTag, PikePass and ExpressToll will work on all PA Turnpike roads. they will not work on the bridges to New Jersey with the possible exception of I-95!

Others

Florida - SunPass, E-Z Pass and and all CUSIOP tags already work in Florida making the state at least Triple Redundant. Yes - EZTag now works in Florida, and SunPass works on HCTRA roads! SunPass would pretty much be the laughingstock of transponders if it weren't for Lee County.  E-Z Pass requires a SunPass PRO or EPASS Uni. and Colorado require a SunPass PRO.  EPass does not work with CUSIOP

Georgia - Peach Pass is interoperable with E-Z Pass, but not with CUSIOP. It had been prior to joining E-ZPass.

[ElishaGOtis]

Intentional Double post

Agencies will not update their information right away. Many take quite a bit of time (months or more) to do so.  CRM and HCTRA are notorious for being stubborn to accept other passes (having put off acceptance of SunPass and ExpressToll for at least a year each)

Here is what each agency is saying regarding the new interoperability between Central US and E-Z Pass network equipment at the time of this post.

E470 - https://www.expresstoll.com/travel-info/interoperability
ExpressToll site explicitly indicates it is operable with the following E-Z pass agencies: MDTA (Maryland), and Ohio Turnpike and Infrastructure Commission, Pennsylvania Turnpike Authority, IN Toll Road Concession, Skyway Concession, ISTHA, NC Quick Pass, MassDOT. NOTE: Northwest Parkway's primary program is GO-PASS. They do accept ExpressToll transponders - but no other transponders (including KTAG, PikePass, TollTag and EZTag.)

KTA - This PDF indicates all of the agencies KTA has set up interoperability with.  MDTA and Ohio Turnpike are not on the list.  The list is accessible through the DriveKS FAQ.  The E-Z Pass agency tags will work on all Kansas toll facilities

PikePass - https://pikepass.com/plan-your-trip/interoperability Shows IL, IN, PA, MA, NC and lists the same agencies KTA did. The E-Z Pass agency tags will work on all OK Turnpikes

NTTA - https://www.ntta.org/plan-your-trip - Scroll down and select "New - PA, IL MA, NC, IN"

Customers regularly tell us they highly value the expanded travel options and convenience their TollTag provides.

Now, TollTag customers can use toll roads in Pennsylvania, Illinois, Massachusetts, North Carolina, and some toll roads in Indiana and receive the lowest toll rate.

WHERE TOLLTAG IS NOW ACCEPTED
•    Pennsylvania Turnpike Commission
•    Illinois State Highway Authority, Skyway Concession Company in Chicago
•    Massachusetts Department of Transportation
•    North Carolina Turnpike Authority
•    Indiana Toll Road Concession Company

NTTA customers using participating toll roads will have tolls automatically deducted from their TollTag account and posted to their monthly statement.

To take advantage of this convenience, drivers must have a TollTag account in good standing.

Vehicles should NOT have both a TollTag and transponders from another state. Please choose which toll account you would like to keep, close the other account and remove that sticker from your windshield.

The E-Z Pass agency tags will work on all NTTA roads. They will not work on other toll roads or any HOT lanes (Central Region Mobility, HCTRA, FBCTRA, TexPress, etc.)

Central Region Mobility (TX) - Does not list E-Z Pass, NC Quick Pass, or I-Pass as an accepted tag.

HCTRA - https://www.hctra.org/FAQ/All Their FAQ only indicates Florida, Oklahoma, Kansas and Colorado as of 7/22/2025.  Please note that TxTag is phasing out in favor of EZTag.

ISTHA- https://agency.illinoistollway.com/about-ipass

Traveling with I-PASS is easier now that it is accepted by toll facilities in 24 states across the country including E-ZPass facilities to the east and new partners in the Central United States.

However, the agency is not specifically stating which other Central US agencies are participating.  And how did they indicate 24 states?  Keep in mind Bay City, Michigan! KTAG, TollTag, PikePass and ExpressToll will work on all ISTHA roads (88, 90, the Tri-State, 355)

Chicago Skyway- https://www.chicagoskyway.org/toll-information/#ez-pass-info
The SCC relies E-Z Pass IAG to indicate interoperability and has not mentioned CUSIOP on their own site. KTAG, TollTag, PikePass and ExpressToll will work on the Skyway

Indiana Toll Road - https://www.indianatollroad.org/e-zpass/
ITRCC has not mentioned CUSIOP on their site KTAG, TollTag, PikePass and ExpressToll will work on the Indiana Toll Road. They will not work on the Cline Ave Bridge or the bridges to Kentucky.

MDTA - https://driveezmd.com/acct-types/e-zpass-regional-network/

Their site is extremely outdated - no show for Michigan or Minnesota much less CUSIOP.  If the information is accurate. ExpressToll will work on the Baltimore infrastructure (HOT lanes, Harbor Tunnel, Fort McHenry Tunnel, Francis Scott Key Bridge - when it reopens)

MassDOT - https://www.ezdrivema.com/AboutEZDriveMA

Does not mention ANY interoperability on the site.  KTAG, TollTag, PikePass and ExpressToll will work on the Mass Pike, Tobin Bridge, Sumner/Callahan Tunnels, and Ted Williams Tunnel

NC DOT (NC Turnpike Authority) - https://ncquickpass.com
if you have JavaScript enabled - you'll get an alert overlay with the following:

NC Quick Pass now works in 23 states. See how far your transponder can take you: view coverage.

They're not counting Michigan!!! KTAG, TollTag, PikePass and ExpressToll will work on all NC HoT Lanes

Ohio Turnpike - https://www.ohioturnpike.org/
A not-so-eay-to-find blurb below

And here's the best part — E-ZPass works in 20 states, so your savings can really add up.

Unless they typo'ed this hints at E470's support.  If the information is accurate ExpressToll will work on the turnpike.

Penna Turnpike - https://www.paturnpike.com/e-zpass

PTC relies on the E-Z Pass IAG to indicate interoperability and has not mentioned CUSIOP on their own site.  KTAG, TollTag, PikePass and ExpressToll will work on all PA Turnpike roads. they will not work on the bridges to New Jersey with the possible exception of I-95!

Others

Florida - SunPass, E-Z Pass and and all CUSIOP tags already work in Florida making the state at least Triple Redundant. Yes - EZTag now works in Florida, and SunPass works on HCTRA roads! SunPass would pretty much be the laughingstock of transponders if it weren't for Lee County.

CFX is the holdout in Florida. None of the central hub tags will work there at the current time. I believe they're the last phase of the E-ZPass IAG integration.

On a similar note, do you guys think any agency within the central hub will rebrand their tag to E-ZPass once the hub goes fully interoperable like what Minnesota did?

[Great Lakes Roads]

On a similar note, do you guys think any agency within the central hub will rebrand their tag to E-ZPass once the hub goes fully interoperable like what Minnesota did?

Probably not. 

[vdeane]

If they were, they would probably just join the IAG and everyone would be interoperable with everyone rather than this happening piecemeal between every central hub agency and every E-ZPass agency.  Remember when an E-ZPass was an E-ZPass was an E-ZPass?  I do.  Now which state you get one from doesn't just determine how much you pay in tolls, but even which roads it can be used on!

[I-55]

On a similar note, do you guys think any agency within the central hub will rebrand their tag to E-ZPass once the hub goes fully interoperable like what Minnesota did?

Probably not. 

I could maybe see something similar to NC QuickPass where they kept the QuickPass branding but added a smaller E-ZPass logo in the corner. The new I-Pass sticker tags also include both the I-Pass brand and E-ZPass logo.

[SSOWorld]

On a similar note, do you guys think any agency within the central hub will rebrand their tag to E-ZPass once the hub goes fully interoperable like what Minnesota did?

Probably not. 

I could maybe see something similar to NC QuickPass where they kept the QuickPass branding but added a smaller E-ZPass logo in the corner. The new I-Pass sticker tags also include both the I-Pass brand and E-ZPass logo.

Highly unlikely. At least in the short term. The Central Hub sets things apart from E-Z Pass and SunPass. Short term, one should still have a tag that is 100% central hub coverage, but that should be TollTag, K-Tag, ExpressToll, or PikePass.  EZTag (HCTRA) is very stubborn about adopting as are many of the E-Z Pass states because both don't have the technology to work with each other yet. NTTA has been the very friendly pass in the Central Hub followed closely by K-TAG and PikePass. ExpressToll's inclusion is too new to judge.

[kalvado]

On a similar note, do you guys think any agency within the central hub will rebrand their tag to E-ZPass once the hub goes fully interoperable like what Minnesota did?

Probably not. 

I could maybe see something similar to NC QuickPass where they kept the QuickPass branding but added a smaller E-ZPass logo in the corner. The new I-Pass sticker tags also include both the I-Pass brand and E-ZPass logo.

Highly unlikely. At least in the short term. The Central Hub sets things apart from E-Z Pass and SunPass. Short term, one should still have a tag that is 100% central hub coverage, but that should be TollTag, K-Tag, ExpressToll, or PikePass.  EZTag (HCTRA) is very stubborn about adopting as are many of the E-Z Pass states because both don't have the technology to work with each other yet. NTTA has been the very friendly pass in the Central Hub followed closely by K-TAG and PikePass. ExpressToll's inclusion is too new to judge.

I can see a few long term limits on everyone coming under the same brand.
first is apparently the tag technology. looks like EZpass is trying to become tag-agnostic, with multiprotocol readers becoming the standard
Second one is clearinghouse infrastructure. Which may be messy, especially once license plates are considered a backup billing option. 
last one is legal. There must be a way to exchange tag data, violations data, possibly license plate and identity data. That can quickly become a mess, state regulations may need to be harmonized.
   

[SSOWorld]

ISTHA updated their interoperability map to full lower 48. showing KS, OK, partial TX, partial CO in addition to the EZ pass states including partial MI.

https://agency.illinoistollway.com/about-ipass

Still no detail of what in Texas and Colorado are supported.

[Great Lakes Roads]

ISTHA updated their interoperability map to full lower 48. showing KS, OK, partial TX, partial CO in addition to the EZ pass states including partial MI.

https://agency.illinoistollway.com/about-ipass

Still no detail of what in Texas and Colorado are supported.

Gut feeling, but this is what I sense from ISHTA in terms of which toll roads is accepted in these two states:

TX- NTTA system (everything else in Texas will be accepted later)
CO- E-470 and CDOT's express lanes (NW Parkway will be accepted into the system later)

[SSOWorld]

ISTHA updated their interoperability map to full lower 48. showing KS, OK, partial TX, partial CO in addition to the EZ pass states including partial MI.

https://agency.illinoistollway.com/about-ipass

Still no detail of what in Texas and Colorado are supported.

Gut feeling, but this is what I sense from ISHTA in terms of which toll roads is accepted in these two states:

TX- NTTA system (everything else in Texas will be accepted later)
CO- E-470 and CDOT's express lanes (NW Parkway will be accepted into the system later)

You are correct on the first one - I had already confirmed that with the lack of evidence in HCTRA's EZTag FAQs. (TxTag is dead and all agencies use EZTag except NTTA.
The second one, don't place any bets on the NW Parkway's GoPass system being integrated. If you had an ExpressToll, you're lucky to be able to use it. Even KTAG, PikePass, TollTag, EZTag, and SunPass are not accepted.

[ObsidianTheFox]

I tried to do some digging into Canadian toll systems' interoperability and it seems like it's mostly an extrapolation of Michigan, probably because Canada's tolled roads are mostly just toll bridges (and the godforsaken 407 ETR). There does seem to be a small consortium of toll bridges in the Maritimes (also including the tolled Cobequid Pass) that are semi-interoperable, allowing the sharing of transponders but requiring separate accounts:

The Halifax-Dartmouth Bridge Commission Macpass, the Saint John Harbour Bridge Pass and the Confederation Bridge StraitPass systems use the same transponder as the E-Pass system. If you already have a transponder from a maritime toll facility you can create an E-Pass account. You do not need multiple transponders in your vehicle.

Note that the E-Pass and MacPass referenced there are not the same as the Florida and Michigan transponders of the same names.

I also found this hopeful tidbit on one of the Quebec transponders' websites (there's two in Quebec):

Is the A-30 transponder system compatible with the electronic toll systems found at the Olivier-Charbonneau Bridge and other provinces or the United States?

The system is not compatible at this time. This solution is currently under consideration.

[vdeane]

At this point, I'm feeling like interoperability between Canada and the US is probably less likely than it was before.  With Canada trying to become less reliant on the US and align more closely to the EU, interoperability almost feels like a political step backwards.

[kphoger]

At this point, I'm feeling like interoperability between Canada and the US is probably less likely than it was before.  With Canada trying to become less reliant on the US and align more closely to the EU, interoperability almost feels like a political step backwards.

interoperability ≠ dependence