You can watch the game trailer here. http://www.youtube.com/watch?v=jjAcA6khIdQ
In this game one player commends the zombie hoard while the others play as the squads sent in to cleanse the city by detonating a nuke in the right place. So for the human players it works similar to a survival map except the attacking hoard isn’t mindless or predictable. For the Zombie player the game is about using civilians to repeatedly mass up (in traditional zombie fashion) as fast as possible and wiping out the humans or at least stopping them from reaching the nuke site safely.
Buildings, mineral patches, and the final beacon are generated randomly each game so each game is a unique experience.
Check it out on battle.net and feel free to comment or offer suggestions.