We have railfanned Fernie, British Columbia several times which is in the Crow's Nest Pass and on the route a great deal of the traffic for the SI passes through. Trains can be heard in the canyon for some miles in either direction. More than once standing trackside near the old depot waiting for some CP action, what were the leading units? Armour yellow UP!. I could have stayed in Ore. and spotted them not far home in the Blue Mtns. While there is certainly a fair amount of CP power especially on trains that will head up the Columbia Valley instead of south, it has seemed to be about 50-50 with UP power on trains crossing the border.
So where does CP have interchange with BNSF? It seems like Bonners Ferry could be a viable interchange point if there was actually a demand.