This is the same way overhere. We have 3 football (or soccer whatever your wish to call it) professional teams near my town. If your from the south of the city your rooting for team A, if your from the west part of the city you root for team B and if your from the north part of the city you root for team C. It's like a Brooklyn vs Queens thingy... My friend and colleague roots for team B, a friend of him roots for team A. Just to poke at him his friend buys a jersey and pants from his team for the birthday of his eldest son, which almost got scouted by team A. I always have to giggle at it. We have about 5 or 6 soccer clubs for the kids and amateurs in town, it's even a competition within our street. I think it's pathetic, although my kids so play soccer, but each to their own. Also there is home and visitors part of the stadium, when I watch gridiron football I see all kinds of jerseys mixed. I once visited a match in Germany, supporters where sitting next to each other and had a big laugh, was a lot of fun.
Edit: sorry for your loss last night, they played really well, better than during the season.