Go-Ahead London use theirs on private hire/rail replacement, as the DTV equipment can be easily removed, presumably set up for that.
However, at a company such as Arriva, ticket machine apparatus and assault screens would have been removed, in some cases, destination displays too. Also, I believe the mentor seating isn't removable either.
I'd say the answer would be no, and a vehicle would be loaned from another depot.
RE: Training Vehicles in Service