He seems to be only running on facebook. Update though, the tunnel network running under the city are now open for play, as is the school and firehall. The school alone is 44,000 square feet of indoor goodness, complete with central courtyard. Firehall has sniper nest. Pics are on the page.
TBH I'm a little sad that this is only running on facebook, as I don't have/use it myself, so I actually made an account specifically for this. He has game rules/ registration and all pertinent information up on the group though. Registration appears to be paypal/emt directly to him, followed by a PM on facebook as to which team you wish to join. As far as I can tell he is also very communicative with anyone looking for further information, and is happy to answer all questions sent his way.