I witnessed one incident in a tri-jet when the autopilot was twitching the controls. A search of the cabin for active mobiles was made but it turned out to be the captain`s `phone in his flight bag. Once turned off, the autopilot gave no more problems. There was also an instance in my company on a B734 where a port engine surge was put down to a passenger in a window seat alongside the engine using his mobile. In reply to an earlier letter about fbw, an A320 was subjected to extreme exposure by a radar scanner centered on the avionics bay while configured in flight mode with engines running. I believe this was continued for several hours and no interference was recorded . This was one area where certification authorities really had to be convinced.