if the project is funded with Public money it should be subject to the Davis-Bacon Act, this requires the employees doing the respective work be paid the PREVAILING WAGE in that area, this is available from the Owner/City, as it was included in the bid documents.
Yes you are correct, I did not know the name of the act. That was one of big complaints at the protest.
UPDATE:http://www.independentmail.com/news/2009/feb/12/protest-city-fire-station-construction-site-enters/
ANDERSON Civil unrest escalated Thursday while protesters stood outside the Anderson construction site of a city fire station and said the workers on the project were not documented as legal United States residents.
I am a Heavy Construction Contractor working in both New Jersey and the 5 Boroughs of NYC, we are 100% Union and I still must report and check to see if the people sent me by the respective unions are citizens or legal aliens, have had a couple illegals come through and no, they do not get hired.