Good inference (not quite proof, but very sound inference), but one little nit. Barnes may have seen the forgeries without necessarily knowing who the forger was.
Sure, that is a possibility, but these were new forgeries. It's not like they were floating around on the internet. Barnes had direct contact with someone in the chain of custody PRIOR TO CBS. How is that?
Lets say Burkett handed them off to some Kerry staffer, then they were brought back to the Texas Kerry campaign headquarters. Barnes was called up by the Kerry campaign: "Hey, can you make some accusations on national TV for us?"
Then Barnes says: "I can't put my good name and credibility out on the line with unsubstantiated claims!"
Kerry campaign: "Don't worry about it, we've got documents! Proof! You will back them up, and they will back up you."
Barnes: "Well, if you've got documents, then ok, I will."
So Barnes calls CBS. They set it all up, and then a day or two later, the documents are sent to CBS. Who actually sent them is of no relevence to the preceding chain of events. Burkett sent the documents to the Kerry campaign. barnes is part of that campaign. First Barnes then the docs come forward to CBS within mere days.
Either it is an INCREDIBLE, IMPROBABLE coincidence, or there was co-ordination between the Kerry campaign and the forger in giving this story and these forgeries to CBS.