That usually happens, next time an alien invasion happens ina neutral or easily accessable location you will see clan and omni together fighting even in the same team group, hell I was in a team in OA durring an attack with one omni in the group... an omni fighting aliens in old athens! And while it may not be in a majorly populated area time to time arks go on little adventures with whom ever is curious enough to follow a greenie around town for a while. just two or three weeks ago i found one wandering around Athens and followed it through neutral and well I didnt follow but met up with it on the other side of an omni area where it led us to an outpost in nowhere to fight an alien recon group.
If that is not enough for you remember that this is AO your playing and not WoW, if j00 w4nt fari3z n dr4g0nz ANARCHY is not for you. In fantasy its easy to say poof a dragon appears in a cloud of mystic blue smoke just ahead of your party... the dragon says "Dost thou have in thy possession a chalice of perpetual thirst?" and not have to have a background to why there would be a dragon in your path. In sci-fi you kinda need the scientific reasoning behind why something is the way it is. (arks are an exception to that rule "/me dissapears in a whirling cloud of nanobots and bright light"
point is each game has its own style, the moment a game gives up its own originality in favor to mimic another game is the time that game ceases to be fun and becomes a knockoff of an original and sold in the heap bin at $4.99.
The secret is that there is no spoon... that there is no fork... there is only the spork.