> There is no threat to rail passengers, unless a passenger train does not know about a stopped train ahead of it on the tracks, e.g., a cargo train go stopped by the hack, but the passenger train 10min behind it did not and continues to rush onward towards the stopped cargo train.

Almost everywhere in Europe uses actual signalling blocks backed by axle counters and DC detection circuits between the rails of a track, or by physical key/token based interlocks to detect if a train can safely enter the block. The way the US does it (especially detecting if a train has not been separated along the way by using a caboose/end-of-train beacon) may cost less money, but would be viable to such issues.