I assume in the same way as the other Quake games are played, with the accelerometer. It would be more of a novelty than anything else and for those like myself that moderate the server, it allows moderation on the go
Even if it is hard to play by the phone itself, think about what you could do by hooking up say a wiimote and plugging it into your TV. We already have a nice portfolio of games on our pocket gaming device, so why not add another one

Cheers