If you watch the screenshots at gamespy (where they are 1920 x 1080 on fullscreen), you can clearly see that there are only fighter squadrons around the Sova.
Normally I would agree, but as the other ones in the lower left look like bombers and the trails are completely different, and there's this:
GameSpy: So they'll function, basically, as a very heavy fighter?
Brian Clair: Yeah, you could say that. They're much larger than a fighter, they have shields and armor and all that good stuff.
Just because they look like a fighter doesn't mean that they aren't corvettes just bigger and more bad ass.
You want to see a corvette? Picture #2, at the bow of the titan above the Cobalt. Look at the gamespy picture. It is easier to see there.
That does not look familiar to me. Might that be the bugger?
Upon further review, I am inclined to agree that this one is now my primary candidate as well.