based on M1 body the cars had either Garret or GE turbines. the cars also had low level steps were the Crew controlled side door is.. the experiment was for a train to get to last electrified station leave the electric M1's and continou with the dual mode turbo units.
the cars were not a great success. they did not have a bubble on top your confused with the UA turbo of Penn fame.
the M1 turbo's looked same but had a huge air intake at both ends of car near roof.