[Sorry for the delay, folks. Had an interview with Obama's top defense advisor, former Navy Secretary Richard Danzig this AM...More to follow on that later.]
At the Modern Day Marine Expo, Adamiak explained that the crew chief will use an X-Box-like controller to move and shoot the gun. The GAU-17 (GAU-2 for the SOCOM version) Gatling gun is slaved to a sensor that rolls down out of the Osprey belly when the gun deploys -- housing a CCD camera, IR camera and laser range finder.
The gun can track 360 degress, but there is a software-driven safety zone that makes sure rounds don't blow the rotors off. If the Osprey has to maneuver away from the target and the crew chief can't hold the gun on the bad guys manually, the system slaves the gun to the point of the last shot, slewing it as the plane moves. The fire control computer compensates for range and angle as well.
There is no capability for the pilot to control the gun, but there's an auto feature than swings the gun to the barrel forward position, 10 degrees down so the pilot can steer the Osprey onto target. But he can't fire the weapon, that'll still be up to the crew chief in the back.