Gameplay in P:UCAG (seriously, super smooth, even in acronym form) is mostly competitive: Two to four players place Aperture test subjects into various testing environments, trying to kill off either their opponents' pawns or their own. The only time players cooperate is when they're teaming up to defeat another, more powerful player.
Hey, if Chell and GLaDOS can put their differences aside long enough to work together, surely board game players won't have to resort to pumping the game room full of deadly neurotoxin, right? ... Right?