The Denver Post has an article on similar union practices in Colorado, entitled Irony marches with union sign carriers.

Unfortunately, much of that article misses the point - even a labor expert quoted in that piece thinks that the irony is that the protestors have no stake in the protest. That may be ironic, but the deeper irony is hidden further in the article. In Denver, day-laborers from El Centro Humanitario Para los Trabajadores are paid $10/hr, which a person affiliated with that day labor center claims is a "living wage."

But scroll down to near the bottom of the article and you'll discover the reason for the protest:

It [the union] wants those [non-union] contractors to pay an "area standard wage" of approximately $16.25 per hour and to provide their employees with retirement benefits, training programs and family health-care coverage. And it's willing to picket those who refuse.

Yeah, the union is willing to picket others but it's not itself willing to pay those who picket the "area standard wage" or give them "retirement benefits, training programs and family health-care coverage."

Union member Gary Ulmer, 48, who was working in a building nearby, shrugged when asked what he thought about day-laborers picketing for the union. "It gives them a wage," he said.

Yeah, and so does working a non-union construction job...

And then there's this gem:
By paying low wages, contractors help depress pay for workers other than their own, said Joe Avila, 50, a union carpenter who pickets because he has been out of work for six months. "This affects everybody, and it brings down the standard of pay and health care."

So, what about unions that are paying low wages, Joe? Why do they get a free pass?