Well, I know that our members, in some cases, have agreements both with traditional building trades and with CLAC. In some provinces they are non-unionized and in other provinces they are unionized. So, very much the same employer uses the labour relations situation, depending upon the jurisdiction, that puts them in the best competitive position.
If you're going to use a brush and say that all those are bad and all those are good, from the employer's perspective you're talking about the same group of individuals. They have a foot in all the camps.
Let's remember that at the end of the day, the quality, timeliness, and efficiency of the construction are all determined by independent third parties that don't particularly care what your union affiliation is.