FM receivers typically use a PLL (phase lock loop) circuit for
demodulation. In the presence of multiple received signals the largest
amplitude one will be locked to and thus demodulated. In AM receivers
all signals present at the detector above a certain noise threshhold
are detected. This feature, while often noiser, allows your friendly
controller to hear two guys calling simultaneously. For voice
transmissions, narrow band FM can be used and equivalent bandwidth
results.

Sorry if this is addressed somewhere in this thread already. I didn't
wade through all of it.