There have been several threads on the issue of handheld devices that could interfere with aircraft systems in the past on PPRUNE.
Bottom line is that many of these devices will emitt at least a small amount of RF, and there have been occasional reports of real interference. Since there are so many different possible emitters and receivers it appears reasonable and prudent to have everybody turn everything off in the back of the bus that is not certified for operation in aircraft. Either that or wrap the users and their equipment in metal foil or mesh and ground it to the aircraft. May not solve the emissions problem but it would discourage users who didn't really need to use because it would be uncomfortable and look stupid.
As far as the US turning off ground based navaids, work it out for yourself: Turn the VORs off, don't have to maintain them. Do have to keep the real estate , telephone lines, electricity ,uildings etc because the RCAGs are colocated. Oh, and you have to get everybody to equip their airplanes with GPS.