Class 185s use shore supply at Ardwick and York TMDs.
It essentially substitutes the alternators and when plugged in forces each car to cross feed. Saves having the engines running all of the time, especially in the sheds.
It powers everything on the 400v 3 phase system, the only limitation is that some functions of the saloon HVACs are disabled (convection heaters for example). The air compressor, cab HVACs, battery chargers, engine pre-heaters, toilet modules and plug sockets operate normally. As the battery chargers operate, so do the 110v and 24v DC circuits too, which means pretty much everything is functional apart from obtaining traction (interlocked).
They also have sockets to allow the pre-heaters alone to be powered at outstations but I don't think they've ever been used. Same goes for the 24v battery charging sockets too.