Earlier quoted context omitted.
The GP's point still stands: if you are within transmitting range of your car, anyone can push the button on the car door and open it. I doubt that the transmitter verifies line of sight between it and the car.
I have a car with that system and in my experience you need to be really close to the car for the system to work. Stand further away than arms length from the handle and the car won't open even if someone else tries to open it. Also it looks like the car has independent antennas on each side - even if I stand very close to the driver side, you can't open the car by pulling the handle on the passenger's side.
I really wish car manufacturers would not rely on security through obscurity for these systems though.