Earlier quoted context omitted.
So, we don't know if this is the case, but one way to do this is not to ask the phones but the cells . The mobile network has to know where the phones are by cell; the cells are often small relative to the speed of the train; there are also cells installed specifically to improve service on trains, or provide a base station to the train wifi, or for communications to railway staff. If you get a bunch of phones switch…
You're missing the fact that the system is also divided into explicit signal blocks and those blocks do report train presence to a centralized system[1]. I am not certain if they want to share that information, but if someone got serious about building a system like signalbox I'd expect that NetworkRail would either offer their data, a degraded version of their data on a lag for security reasons, or consider those se…
though interpreting it isn't the easiest thing in the world...