This has been hinted at before but Gearbox boss Randy Pitchford wouldn't reveal specifics. A job ad for TimeGate mentioned level design and the user interface.
The listing said that TimeGate were "looking to expand its team of ultimate badasses working on Aliens: Colonial Marines," and specifically mentioned game level design as well as the user interface. The job ad has since been removed from Gamasutra, it appears.
TimeGate Studios developed Section 8 and its sequel which are both multiplayer focused FPS. They also created the Perseus Mandate and Extraction Point expansions in the F.E.A.R. franchise. Pitchford said TimeGate were "development partners".
Aliens: Colonial Marines releases on Xbox 360, PS3 and PC early next year.