let me make sure i am understanding you. two gms. two groups of people. two games. same world. events ripple and interact?
if so, then yes i've heard of this. one group was the heroes, the other group was the villains. they met in a huge day-long session for the epic final battle. the groups didn't know about much about each other except the fact that other groups were actively running real time in the same world as themselves. everything else was learned in-game. i understand that it was very satisfying all around.