The two NJ engines, 4050 and 4051, were built by Montreal Locomotive Works, an Alco subsidiary. They were allowed by the US to operated into the US only on assignments that worked into Canada, otherwise the D&H would have to pay US import duty on them. The same rule applied in Canada regarding US power.

Heavy repairs on the two NJ units were done by CP at Angus Shops in Montreal. If the D&H replaced any parts on them the NJ would have to pay import duty on the value of the parts.

I remember one cold night at Rouses Point when Train 35 arrived with a single unit that had to be taken out of service and replaced with the RO yard engine which had a steam generator for train heat. It was standard practice to assign a passenger unit to RO Yard to protect that service.

Then the only unit available at RO was the NJ 4051. The yard crew had to finish building RW-6, and WR-1 had not arrived with its power. So certain arrangements were made with the US Customs officers at RO to look the other way for a few hours while NJ 4051 finished building the train for RW-6. International commerce was handled with little interruption.