As the RAIL piece says:

Network Rail has served West Coast Railways with a suspension notice effective from midnight on April 3.

It follows the Signal Passed at Danger (SPAD) on March 7, when a 100mph collision between a First Great Western High Speed Train and a steam excursion operated by WCR was missed by barely a minute. The SPAD ranked as the most serious this year.

This is an unprecedented suspension. Operators have been banned from certain routes, but this is the first total network ban since privatisation, indicating the gravity with which Network Rail is treating the incident.

West Coast Railways provides crews and motive power for charter trains across Britain, including the well-known Fort William to Mallaig run, and this suspension is likely to force the cancellation of many steam specials on the main line in the coming weeks. Two scheduled for this coming bank holiday weekend have already been cancelled.

There have been incidents where a bus company has had its licence suspended after a fatal accident revealed serious issue with driver training and the roadworthiness of their vehicles. But nothing like this has ever happened on the railways.