But which should also open up UMG and / or YouTube to the restraining order which MegaUpload have asked for. If the takedown wasn't anything to do with the DMCA, then they can't invoke DMCA rules governing penalties for abuse of the takedown system.

So, far as I can see as a non-lawyer, UMG are in trouble either way. If it's a DMCA request then they've perjured themselves because they don't own the content. If it's not a DMCA request then they're open to standard civil court provisions and restraining orders, and will likely get sued for restraint of trade or similar.

Yeah, I wasn't questioning that. I was simply stating it, one because I find it hard to believe that YouTube would sign such an agreement and second because it means an corporation can censor what they deem to be damaging for them.