I'm not sure you're right, legally speaking. At the very least it's a grey area. I certainly have the "reasonable expectation of privacy" (the legal test) in a hotel room that I don't own - a hired car doesn't seem that different to me. When you see an actor get into a car to avoid the paparazzi - they rarely own the car, and reasonably expect the driver not to film them and upload to TMZ or something. (IANAL, TINLA)