Did something similar at a former employer except we played Counterstrike. The aim - though I never stated it - was to try and knit disparate teams together. While their code integrated the people often didn't. I was just a lowly QA dude back then but it was pretty clear when it started that the games run after hours were actually getting people talking during hours. The Dev and QA guys who played formed closer ties, there was less throwing of issues over the fence and we got talking about our work both before and during games (server load time wasn't great back then). The team integration was better too - problems became shared rather than this or that teams' issue to deal with.

Plus we got to waste a couple of managers who ventured into the territory :) There were no boundaries - just talk to someone and you were in or send a mail to the inhouse CStrike list.

CS isn't as easy to get the hang of as BAB of course, one of the main blockers I suppose to participation. Plsu you had to be interested in gaming to want to play, but the good thing about working with nerds is that most of them have at least been gamers in the past, if not active currently.