The choosing not to compete is the outcome of the oligopoly. That’s what it is, and it’s outcome.
Bell knows that if they leave that area to Roger’s, Roger’s will leave this other area to Bell, because it’ll cost both of them too much money to move into the other spot and lower their prices, when they both can reap the rewards of not competing in that spot. They don’t have to worry about anyone else because it’s mainly just the 3 of them, Telus, being the other.
Moving into a building with only 1 choice sucks and should probably not be allowed if it’s a contracted thing.