I notice today the former depot is back open as a car park. So if you want to park your car in the same place where Atlanteans and Olympians once parked, now’s your chance.If we're talking subterranean bus depots, then Bradford Interchange would count. The bus station is above and the bus depot was in the basement. There was no direct link between the two.
The basement depot was always completely unsuitable and I'm amazed it took Yorkshire Rider/First as long as it did to move out. It was a car park for a bingo hall for a while and now it's empty.