I was in LA last week (vacation + rental car) and Google Maps definitely sent me to the express lanes on the I95 every time. They had the exact knowledge of the entrances and merges back.
As an aside, yesterday I was traveling upstate NY and to get off from I87 to some local road, Google Maps navigated me to a "Tandem Area", which was also marked that way by a sign and was indeed the right choice. Of course, I'd never turn myself from a highway to a Tandem Area ;)
So it seems like they have a lot of small detail knowledge.
As an aside, yesterday I was traveling upstate NY and to get off from I87 to some local road, Google Maps navigated me to a "Tandem Area", which was also marked that way by a sign and was indeed the right choice. Of course, I'd never turn myself from a highway to a Tandem Area ;)
So it seems like they have a lot of small detail knowledge.