Looks to me like someone(s) likes to argue more than they like to work.
Come on ... a rocker who can't be bothered to do the cut-outs? If that's not part of his job, I don't know what is! In the abstract, I could see his point, if he bid based upon few outlets, and many were added - but that's still no excuse for deliberately burying them.
The reasons for backcharges include providing an incentive for things to get done ... and to move the money around if they don't. so the guy who does the work gets paid for it. If you do my work, I get to pay ... it's that simple. Backcharges should NEVER be passed on to the customer. Nor can I imagine any court enforcing them upon the final customer.
From the tone of your post, I get the idea that there is more work available, than there are folks to do it. If that's the case, it's time to 'fire' this GC, and get another. It's either that .... or double your price, to include putting 24" of rock around every box. (I'd like the rocker try to claim he can't tape to your rock!)
