I get a bit tired of saying this (because a search of this website should reveal plenty of previous discussion on the matter) BUT a mobile phone on a UK network will set off the Aft Baggage Smoke/Fire warnings on our aircraft (S-76).
There is no fire extinguisher system in the bay so if this occurs, the Emergency Checklist requires us to land as soon as possible. This may mean landing in the nearest farmer's field. If we are IMC at the time, this is a very awkward situation.
The 737 pilot's answer is worrying and seems to stem from ignorance of the broader picture. He should be asked how he would feel about un-certified electrical transmitting equipment being used in his aircraft.....
We specifically emphasise that phones MUST be switched off before flight. Pax wanting to put luggage in the baggage compartment are asked to confirm that any phones therein are removed or switched completely off.