Happened before at a smaller scale, crazy high redundancies in GSM-R mean this is likely sabotage:
https://en.wikipedia.org/wiki/October_2022_German_railway_at...
https://en.wikipedia.org/wiki/October_2022_German_railway_at...
My personal suspicion, GSM-R is 90s GSM, they'll likely have a fried HLR & VLR because in any GSM network these are fundamental, without them you can't even get roaming from public phone networks working as there is no way for the public network to authenticate GSM-R subscribers.