Hi,
I have had great pleasure recently running my Rapido FP9A with Walther's Ph.II Amtrak cars around a Bachmann 22" radius oval - beautiful. I imagine it is a Toronto - Buffalo,NY train in the 70's - would this ever actually have occurred?
There was a jointly run cross border train from Chicago to Toronto called the "International". In the 1990s it wasn't uncommon for this train to run with a VIA F40PH-2 and Amtrak cars. I've seen photos of a VIA F40PH-2 on this train hauling Superliners, which VIA did not own. This train was cancelled around 2005, although in the later years this ran exclusively with Amtrak equipment. I don't know about consists for this train in the 1980s and 1970s, or when it began operating, although I have a photo from the early 1990s of the old VIA blue coaches heading through the international tunnel at Sarnia.
There is also a joint train from Toronto to New York (via Niagara Falls and Buffalo) that is still running today. This also currently runs with exclusively Amtrak equipment. I don't know about what practices may have been in the 1970s. (Note that both VIA and Amtrak were only created in the mid to late 1970s to take over the passenger operations of other railroads, so most realistically this would be representing a late 1970s-early 1980s train.
So basically, short answer: Yes, this is not too implausible, since there actually is a jointly operated Toronto-New York train. I don't know if this operated with mixed equipment, but pooled equipment is possible. I know earlier CN/GTW/LV trains operated with pooled equipment. I can try to find out more information about earlier operations of the "Maple Leaf" from some people I know that probably would have opportunity to actually know this firsthand, living in the Hamilton-Niagara area during this time frame.
Chris van der Heide
My Algoma Central Railway Modeling Blog