Apart from the old analogue cordless phones, and perhaps a cheap doorbell, I would have expected decent remote control systems to use a digital code to avoid mis-operation.
Going into a car park and finding someone elses car unlocking I think very unlikely. It's certainly never happened to me. This isn't down to (just) the frequency, but the need to match the preset code.
I've heard stories of car control systems being blocked by powerful transmitters nearby, simply overloading the receiver, but never of actually operating due to the interference signal.
Is it really a remote start on the car? Sounds potentially dodgy to me! Certainly ought to be protected from operation by stray RF signals.
