Whenever I try to join a game with someone it always starts a new lobby. It never tries to put us into an already started game. It can be kind of frustrating when playing late at night when there is "low activity" because if you start your own lobby it can take forever for anyone to join.
I heard that Ubisoft is "aware of the problem" and is working on it but does anyone know if they are going to update and fix soon?
If you do want to play with friends and not have to wait you can join a game by yourself and pray for open slots and invite your buddies. The catch is that you aren't guaranteed to be on the same team.