[squeaky-clean]

ZipCar has keys in the car and it's part of the service rules that the key CANNOT LEAVE THE CAR. I have no idea if they use rfid or something to check, but I felt it was really clear in their "how to use" videos that the keys never leave the car, you can can get banned from ZipCar.

So while there are keys in the car that you could have held onto to use during a cell service outage, you're told to never remove them from the vehicle.

[parliament32]

That's pretty dumb. Car2go (Vancouver) has keys in the glovebox in a special holder-device: you're free to take the keys with you if you want to keep paying for the car as it's parked, but it won't let you "end session" or whatever unless the keys are replaced into the holder thingy.

This also avoids some of the problems mentioned in the above article. I assume they have a remote-kill but unless there's a serious problem, you always have the keys so you can always start the car.