I had a Camponotous colony with three queens once. They just stayed in seperate part of the nests generally. It's not uncommon as I have seen it a few times myself and in others videos/journals.
nurbs also has a three queen colony.
Had several C. vicinus with three queens (sold one, down to two), and two remaining colonies with two queens. They are the C. vicinus RED variety.
Interestingly, the BLACK variety of C. vicinus do not get along and tear each other apart after they get workers or when you try to place them together. It's as if the REDS and the BLACKS were different species, but when you key them out they are all C. vicinus. I find this both odd and fascinating.
C. vicinus are the only species here in CA that are polygynous --- or so I thought! Then the other week, was reading a research PDF on another Camponotus species in CA that was also found to have multiple queens in the wild. I won't say which species (it's not your usual suspects), but I am going to try and rear them next season with multiple queens.