I guess this was a joke. They can look through the data stored on the servers for as long as they want; they won't find anything because they don't have the keys.
So they can pop in and remove it, just to have it reappear ten times. It will be completely futile waste of time, unless Mega lets them automate this process somehow.
Chances are that the most widely distributed things will be on centralized sites (e.g. ThePirateBay). The RIAA/MPAA could probably easily write a bot to scrape these sites for access information and then go into MegaEncryptedUpload and remove the files.
