I don't know the specifics of New Brunswick, but generally speaking I would guess that they are spending less proportionately on renewal and more on expansion. This could either be a result of having a younger network or greater willingness to let their system age.
For comparison, NB's highway capital construction budget is about $150 million for 2017-18. Ontario's is $1.4 billion.
And if you want to see highway widening projects that are of questionable warrant, justy take a look at 11 north of Huntsville, 11/17 east of Thunder Bay, 17 west of Arnprior, or all of Hwy 69. 
For starters, New Brunswick and Ontario are like comparing a pebble to a boulder.
$150 million for a capital construction budget is impressive for a province which has just 750,000 people living in it. We are over 14 million give or take, so 1.4 billion is practically half their budget per capita.
Here's a map of NB traffic data from 2012:
http://www2.gnb.ca/content/dam/gnb/Departments/env/pdf/EIA-EIE/Registrations-Engegistrements/documents/EIARegistration1474/EIARegistration1474-AppendixF.pdfNew Brunswick Route 11's main cities it passes through are Shediac, Miramichi, Bathurst, and Campbellton which is a border town with Quebec.
Here are the populations of these "cities":
Shediac - 6600
Miramichi - 17,000 (metro area 27,000)
Bathurst - 12,000 (metro area 30,000)
Campbellton - 7,400 (metro area 18,000)
Essentially, one can think of a freeway version of NB-11 being a parallel alternate to NB-2, in a sense like how A-40 is parallel to A-20. It doesn't end there, New Brunswick is determined to then connect Miramichi and Fredericton by a freeway version of NB-8, as well as NB-7 having a freeway from Fredericton to Saint John.
The comparisons to Ontario examples aren't entirely fair, Hwy 11 north of Huntsville leads to a place larger than all the ones I mentioned, North Bay and even onwards to a smaller city but still larger than those mentioned, Timmins. Same goes for Sudbury and Hwy 69. As for Hwy 17....well remember that eventually that route would reach North Bay as well, an easy passage from Ottawa (not a small city like Fredericton) and North Bay.
As for twinning NB-11, I think at the very least, that there's a stronger argument for twinning Hwy 7 east of Peterborough.