Just day dreaming. Russian rail lines use steel rails. Ok is there a cheap way to destroy 100’s of rail miles? Maybe. Thermal shock can break steel. The dragon drones use super hot metal and it is relatively cheap. So drop a dab every 10 meters with drone. Follow with a second drone to drop water on the hot spots, so extreme thermal shock. Then when a train attempts to run on the rail it won’t support the train.
Of course I don’t know the detailed economics but if it turns out to be cost effective this might be a useful technology.