Well you can see DMC did not really make it; FFG did. They are a Hamburg based company, I believe at the time a maintenance company for the Hamburg public transport company. FFG made, as said, the prototype for the Bombardier busses as well and are based on German Standard Bus specifications.
DMC was a New York based company, eventhough they made the cars (for political and financial reasons) in Northern Ireland. As such, they thought they could make an extra buck by making busses. I believe the bus was supposed to be actually made in the US, though others say it was actually thought to better use the factory in Dunmore. Engines for these busses were 6-cylinder diesel MAN or Mercedes-Benz ones. FFG means Fahrzeugwerkstätten Falkenried GmbH