They can have the season across the whole of the continent provided they are able to start it in april/early may and end no later than October/November. that provides a fairly long season and means games could be played in new york, toronto, denver etc. the length means that they could also accommodate an international window for the North American inbound tests. if the rumoured locations are correct (including calgary, salt lake, and denver) the season will have an april start.
If there are two canadian teams, the will be going to two of the following cities: Vancouver, Calgary and Victoria. if the season will accommodate calgary, I would bet a team will be going there along with vancouver.
Canada has a semi-professional system up and running and as we know from recent news, the USA is about to get theirs going.
the oil money from calgary and the real estate money from vancouver that backs rugby is significant. Victoria, while a city of only 370,000, is the heart of rugby in canada and there are enough millionaire businessmen and real estate developers there, who are rugby tragics, to support a team. i've heard rumours that there are plans a foot to redevelop victoria's royal athletic park into a permanent seating stadium of 15,000 and to upgrade the facilities . These are fairly new rumours so perhaps it is linked. Vancouver team would probably play out of Empire Stadium in East Van - a 20,000 capacity stadium specific for rectangular sports. it was recently refurbished to accommode the CFL's BC Lions whilst BC Place Stadium was getting refurbished.
I think the western focus is critical given the extensive costs of operating in north america. ultimately, the middle of north america doesn't much play the game. the western half in both countries is where the game has its largest following with a few exceptions (notably newfoundland in canada...a canadian tasmania that is fanatical for its rugby)