I really have no idea what I'm talking about here, but bear with. I recall that Teletext was provided by "piggybacking" on to redundant capacity in a standard TV signal. Are there rail systems (track circuits? signalling cables? electrification infrastructure? etc) that could, if the will was there, be used to provide a carrier signal for reasonably reliable, fast wi-fi? If so, could this provide a real competetive edge against the airlines?