Ask the cg guy! Probably with 2.2 gamma because most 3d apps dont account for this in view port. Besides its not granted he needs to know the unlinearness, especially if he does not use global lightning. But then again he might use a lut on his viewports. In any case you should write him instructions on the condition of the images.
PS. not all cg guys are so intimately tuned to this kind of color workflow that they understand this so you might have a talk with him regardless.