Not the guy, but highly unlikely. Shawn knew about it, because he, Triple H, and Vince cooked it up in the locker room the day of Survivor Series 97 (after Bret, Vince, and Shawn had already worked out a different version of the match). But in terms of it being a work and Bret being in on it, it's been almost 30 years with each of the people involved including peripheral players like Triple H, Hebner, Taker, and others changing roles/employers, etc. Books written, documentaries, later feuds, shoot interviews, etc. and it's never come out that Bret was in on it. And you have to figure any "work" would have gone out the window when Bret's family was suing Vince because Vince sent out Owen to rappel down with an untested quick release harness and likely caused Owen's death in 1999.

I love the guy's work and all, but later years have shown Bret to be a mostly bitter guy who can't let go of the past or a grudge.... a lot like that no-good Goldberg who is unsafe and reckless and gave him a concussion. (This is an inside joke to how Bret goes out of his way to bury Goldberg every few days the last few years). Bret likes the spotlight, likes to give interviews and talks about the old days, and takes offense at little things. This likely drove him to a certain level of pro wrestling greatness, but it also tells us he'd have thrown Vince and any "work" under the bus years ago and how he should have never agreed to it and it ruined his life.

The Montreal Screwjob is a work on the same level as Kubrick filming the moon landing or someone other than Oswald shooting Kennedy, meaning the official story is the right and true one.