Long time watcher, first time poster.

I've been tinkering with the idea of a "shared campaign" for a while now, and wanted to know if anyone's run anything like it before, and what it was like. I'm trying to go beyond simply "collaborative worldbuilding", "assistant-GM", or taking turns as being the GM (rotation).

Rather, I'm thinking of having two dedicated GMs running, each with a separate and distinct group, but the GMs are using the exact same world as reference. So the two groups of players are playing in the same world together, and can influence the other group's story (as allowed by the 2-GM council), and perhaps even cross paths on occasion.

A cursory search of the compendium of truths (google search), revealed nothing about this style of campaign. Anyone seen something like this before?

Happy hunting,
-Machination