I rent from Hertz, I rent almost weekly and often get car's with their "never lost" system - same thing, different brand. But it seems like I recall hearing about one rental company that's putting on-star in most of their cars???? I just can't recall which one.
The car's that I've gotten "never lost" in were all "premium" cars at Hertz, but not all "premium" car's have it. I know you can request it for an extra fee, I just take what I get.