Whichever....
If he just said “advantage” then I guess he's implying that the union-free contractors are, by their nature, advantaged over the unionized ones. That's not my suggestion; it would appear to be his. I believe all of them can compete on a level playing field but it's news to me that the NDP believes otherwise. It might want to take issue with the unions, if it believes so.
He also suggested that the Merit Contractors Association and the Christian Labour Association of Canada contractors want to block building trades. Do you want to block building trades from competing?