Safety center could make a call, but in general the ARC owns a mishap - even if another squadron's pilots were flying it (unless you had a MOA saying something different).
I'm just going off of my memories from ASO school and it's been awhile since I read the 3750.6. The situation above is obviously pretty in the weeds, since it's an aircraft externalling another aircraft. I always thought that the aircraft that does the damage is the responsible one, but like you said, the best thing to do in this case would be to call the NSC and ask them.