Megavideo would, they hold the rights to the song and have agreements with the artists in question. UMG would be held responsible since their name is on the infringement notice.
Not sure you could imprison a company though. That'd probably be the same as the death penalty.
(Proving that any given corporate officer had the requisite intent to commit a crime (the 'mens rea') is difficult to impossible, which is one reason why corporations can be tried in criminal court.)