I-15/Tropicana interchange rebuild

[mrsman]

but they do generally encourage buses on the HOV lanes.

Buses in CA *love* the HOV lanes. Even outside of HOV hours, buses will camp in the left lane holding up traffic (at least here in the Bay Area). It might be that it's safer for them to use the far lane like that rather than a middle lane where they have to contend with traffic on both sides.

Not only in CA.  Same in WA.

In many states buses are permitted to ride the HOV lane even if they are empty of passengers (i.e. the driver is the only person present and he is running empty before or after completing a shift and heading back to the bus yard.)

[SeriesE]

I think the justification for buses in the HOV lane regardless of the number of passengers on board is so they can better keep to their schedule.

[stevashe]

Also, in WA, there are a number of bus stops that are accessed from the left side of the freeway, specifically so that buses can use the HOV lanes.