I assume that the final treaty would have to be public, which raises the obvious question of why the drafts should be secret. Perhaps the media industry lobbyists don't want to be embarrassed by any proposed copyfascist terms that end up getting dropped from the final version. Or perhaps the negotiations are secret to prevent people from linking each treaty provision back to the company that proposed it (collective deniability).
If you have forewarning you can prepare a defence. If they spring it on you it can be voted in before people have managed to be informed about the content and repercussions.
I'm going to guess the normal news sources aren't exactly going to go out their way to tell us how their parent companies want to steal from the public domain that which should already have been released and to worsen the copyright deal still further for new works that are created.
