I've got a cordless Logitech joystick operating at 2.4ghz - the only problem I noticed once is that the gear of the plane I was trying to land at LHR in zero viz was lowered automatically when my mobile rang. Not sure if the mobile actually caused the subsequent and inevitable crash [but I didn't answer it very politely]. Not even sure if mobile phones operate on or near that frequency - or maybe, as you say, it was a third-party transmission.
