Montreal's Olympic Stadium had players benches on Opposite sidelines as per pic below.
BC Place did have benches on Same side so that both football and soccer fields could share the same opposite sideline. They repaint the lines for Lions and Whitecaps games obviously so having One Common sideline for both sports does save.
The MLS field is about 5 yards wider than the CFL field. So one sideline is common for both fields.
However its a case where Corporate BC Place, run by Pavilion Corporation, is telling the BC Lions and CFL the way things are to be and it shouldn't be that way.
For MLS Soccer it doesn't matter cause by convention, teams benches are on Same side anyways.
So for Whitecaps games, benches are on the Same side, have been as long as I remember.
In Calgary, Edmonton, Regina and Winnipeg, CFL benches are Already on Opposite sides. Correct me if I'm wrong.
And Regina's and Winnipeg's Stadiums are Newer, were built after BC Place was opened in 1983. So contrary what the maker of that Video says, at least in the West, this has nothing to do with Grandfathered rules laid down from regional leagues that existed before 1958.
I already posted a pic from the 1963 Grey Cup at Empire Stadium in Vancouver; benches are clearly on Opposite sides.
Here you see clearly in Montreal's Olympic Stadium the benches were on Opposite sides. What an Amazing pic too ! Grey Cup in Montreal, 65,000 fans !