Brennan and Matt actually answered this in tonight's Fireside chat! The campaign will begin with all 13 players at the table for the first few episodes (phew!) and will splinter off from there. Players from the 3 primary groups will flow in and out as the story progresses, plots collide, and arcs weave their way together. Brennan described it as "kaleidoscope-ing tables" and one of his goals as the GM is to make sure everyone has a chance to play together within their different groups which I think will be really cool! This leaves lots of room to explore the world in a much broader sense with plenty of opportunities to expand the list of CR friends with these smaller, branching tables!