There's one important detail left out of the story. Are the 12 batteries of christmas PN ES17-12 or are they different?
If they are ES17-12, then per this Q/A, they are legal:
http://forums.usfirst.org/showthread.php?t=1682
I'm curious as to what the penalty is for breaking a Robot rule after the robot has passed inspection. I would think that a DQ would be the correct call if found immediately after the match, but they may have already advanced several rounds into the playoffs by the time it is discovered.