"BA SOPs require all mobile phones and PEDs must be turned off for CAT III approaches."
For takeoffs as well when low vis procedures are in effect.
Several years ago into EWR in good weather we had a straight forward 40 degree intercept onto the ILS. The autopilot made a complete mess of it with several 35 degree bank angles to the left and to the right before it finally established. I have no doubt this was electrical interference and most probably came from a PED on board.