I second the need for universal house rules; good call, Horsemen.
As for city, I'd propose somewhere well known so we all have the source material to work off of. Seattle is a tried and tested mainstay, as is Denver and Manhattan. Either of these would work as far as I'm concerned.
I'd be loathe to have teams go up against each other, to be honest, but I'd like for teams to see the effects of the actions of other teams. So, while two teams might go to the same building, maybe they're not there at the same time or if they are, maybe they are at different floors. Or, maybe one team is sent in to clean up after another team that just blew up a room, or something like that.