I haven’t been to southern B.C. since these changes happened so I can only make educated guesses, but I suspect you are correct about additional congestion at choke points like the Fraser River bridge. I do know that CN expanded the Kamloops yard in preparation for this additional coal traffic but I’m not sure exactly how day to day operations go.
While I’m not sure if they officially have trackage rights, CP has had access to North Vancouver for a long time, many of their potash trains go there and so did Teck’s coal trains before this new arrangement took effect. CN interchanges many grain trains to CP at Coquitlam, I’m not sure if CP does the same or runs theirs right through to North Vancouver as well.
An aside, I instantly recognized the second photo in that article. It’s the north switch at Teck’s Cardinal River mine, this point was also the highest elevation reached by any Canadian railway. The orange cone on the right was a marker both for the fouling point and where you would be when you finished loading. The track ends exactly four unit lengths past the switch. I hired out there and worked that line for the first portion of my career. Long tough trips, especially in winter, but I still miss it.