For the last couple of weeks I've been laying tracks for the Yarmouth Sub. I've just finished laying the Yarmouth yard as it was in the 1970s and kind of ran out of information on what's beyond the yard. I have the tracks down as far as where it turns into CN I believe, between South and Public streets.
I have no maps that show that CN had for tracks, what customers were served by who. In the wiki there is an annual report from 1968 that list all customers served by both CN and the DAR, giving the number of cars handled by each railway. I would guess that somewhere there was an interchange track but it's also possible that each railway used terminal trackage rights and served every customer in Yarmouth, no matter what railway they were on. Anyone familiar with the operations of the two railways in Yarmouth? The annual report lists customers that are way out on Bunker Island... that's really stretching terminal trackage rights unless the car was just interchanged to CN and they spotted it.
I suggest contacting the Yarmouth County Historical Society. I know for a fact they have more CN photos which have not been added to hswdpi.ca, because I got photocopies a few years ago. They might have maps of the CN yard as well.
Also, topographical maps, available from Service NS from the appropriate time period show tracks.
