While I understand that the car bluetooth takes control of the phone if no bluetooth device is already connected to the phone, why would it pair with a new device just because it comes into range? Is this just an iPhone problem? Do Android users have this as well?I can't imagine this being a problem with the car, but rather a problem with the phone. The phone knows about all the Bluetooth devices and which one to send the audio signal to. The car is only a dumb mic/speaker, just like your wireless headphone or speaker. I have to believe it's the phone that decides where to route the signal.
I suspect that the phone sees the car come into range and decides to switch sources. I can't imagine the car has the ability to 'reject' the connection because the fobs are not in range.
I could be wrong, but it doesn't make sense to me otherwise.