John,
I can imagine what an average passenger would say if asked if his phone was GSM or CDMA. He would probably say "I think it's a Nokia, mate!"
A live phone in the baggage bay of our heli puts on the "Aft Bag Smoke" warning caption. It's no myth.
As there is no fire extinguisher system fitted in there, the drill is to land asap, not nice if IMC. We always get pax to turn phones off and explain why.