I happened to be in the right seat of an SR22 fresh from the states for a test run a couple of years ago. The pilot had a plan in the GPS and slaved the autopilot to the GPS. He then fired up his mobile phone, hooked up his laptop and checked the weather at our destination. At the same time, he had the VOR tuned to the outbound radial. There was no fluctuation from the needle. He could easily have had the autopilot hooked to the NAV and there wouldn't have been a problem.
My point is that mobile phones continue to be used by GA pilots in flight with no detrimental effects on IFR navigation.
It is becoming obvious that neither side of this arguement can claim to know the definitive answer.
Walrus