Is there a reason a location tracker can't be self contained with it's own power supply and no connections to a plane's telemetry feed?
http://en.wikipedia.org/wiki/Air_France_Flight_447#Underwate...
> French Bureau d'Enquetes et d'Analyses (BEA) chief Paul-Louis Arslanian said that he was not optimistic about finding them since they might have been under as much as 3,000 m (9,800 ft) of water and the terrain under this portion of the ocean was very rugged. Although France had never recovered a flight recorder from such depths, there was precedent for such an operation.
Crashed: June 2009
Black boxes found: May 2011
One way in which I would stress test new electronics designs for resistance to such interference was to stick a mobile phone on top of it and then call that number. Worked like a charm most of the times: instant crash.
I think this is the key point. This isn't iPhone level technology, this is closer to Space Shuttle technology, where things need to be tested to the extreme, radiation tolerant, and able to withstand the force of a literal plane crash.