Something of an emergency service has been cobbled together using other operators.
To their credit, First managed to cobble together some battered old coaches from somewhere and have been running them (for free cos no ticket machines) on some routes (the 21 park and ride and X39 route at least which are running as combined services).
The accident was at 3am which suggests to me that someone at First found out about it soon after it occurred, realised that it was going to last a while and used the early morning to find some vehicles and wake up some standby drivers. Well done whoever that was.