If I remember correctly, this was the 2fort equivalent of payload race, everyone wants to play it because everyone is playing it.
Basically your team is trying to capture all of the control points, but in order to get to those control points, you have to be on the ship to drive it and get it to the point, once there, you and your team must capture the point before the enemy gets there, otherwise, it's just king of the hill.
TL;DR: It's a moving king of the hill with both teams trying to capture all control points.
Again, it's been a while since I've played on a community server besides the Hightower server so I could be wrong at some points.
Or I could just be thinking of something different.