[Animats]

The communications system is not novel. It's GSM-R, which is good old 2G cellular with some special railroad features. Both voice comms and signalling run over that system. Since both went out, the comm system must have failed.

[YouWhy]

Do we know for certain that a major cause of the failure has been a GSM-R failure?

Industrial grade communication systems tend to be very well behaved in terms of fault detection and management. I'd be very surprised if the whole whack-a-mole dynamic described in the post was a failure mode of GSM-R system per se.

[Animats]

> Do we know for certain that a major cause of the failure has been a GSM-R failure?

Train drivers lost their voice connection to their control centers.