He just lost the Impact championship recently, so he can't be tied to a Lucha Underground contract like so many others were, or else he never would've been Johnny Impact in the first place.
LU arbitrally allows their contracted wrestlers to work TV with promotions AAA is friendly with (Impact, MLW) and can threaten them against working with promotions they're not friendly with (ROH).
Hey, look at it this way....if Scotty does wind up coming back from neck surgery only to be fed to A-Train on Velocity....it means that A-Train has been bumped back down to Velocity and is off Smackdown! Maybe Scotty should just take one for the team...