It's supposed to be some type of hidden game mode. Looks pretty fun

Here is a video of it:

This on is on Terminal
http://www.youtube.com/watch?v=ghAYXRHLUWg

This on is on Highrise
http://www.youtube.com/watch?v=_2kQyae-reY&feature=player_embedded#


It looks like Domination with only 1 Flag. 2 teams try to capture the nuke, and once you activate it, you have to get 100 points to set it off. However in order to get to 100 points you or someone on your team have to be close to the nuke. It also seems as though they put the nuke in the hardest to defend area of the map. Expect a lot of dying and a lot of people sniping the person at the nuke.