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/GSM-R

I wouldn't be surprised if it turns out to be incompetence at this point.

If you know anything at all about the Deutsche Bahn, you'll know that it's most likely self-sabotage, in other words, incompetence.

Current suspicion on the German rails reddit is a software update gone wrong.

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.