"Utilizing local Hyperspace Gates and high speed Transport Frigates to reach the front line, the Vaygr constitute a high speed, flexible war force." - Official Site

"It isn't." - Cei Gladstone, Programmer, when asked whether the Transport Frigate was still in the final game.

This ship appears to be the "Transport Frigate" mentioned in the text above; it would seem to be the Vaygr equivalent of a Support Frigate; there are bays for fighters. What function it might have performed is not clear, since fighters don't have fuel in HW2.

The word is that the Support Frigate and Transport Frigate have both been removed from the game since E3.