I've heard some debate on whether it was or not. I thought it wasn't, since they said it wouldn't be connected to them and Colossus is different (his metal form looks different, and he's metal all the time), but I've also heard people saying it is part of that universe.
(Origins was already believed to be non-canon so Deadpool in that one isn't a factor)
So I'd like to know once and for all, is Deadpool set in the X-Men film continuity (obviously the revised timeline, especially with his mention of alternate timelines), or is it its own universe?