DS - I work for a public agency in the Los Angeles area. On most of our projects, we require all contractors to pay prevailing wage rates to all their workers. In order to minimize the instances of 'cheating', we require the contractors to submit certified payroll records monthly, which are audited, and we have people occasionally visit with the workers on the jobsite to ensure everything is OK wage wise.
There are actually 2 different prevailing wafe rate determinations for our area, the federal and the state each have their own. Contractors have to comply with which ever one is higher. I don't know about NY, but checking with your state website might be an idea.
On our projects, the only workers who do not get the basic (journey level) prevailing wage rate are those who are enrolled in a state approved apprenticeship program. Contractors aren't allowed to have 'helpers' outside the apprenticeship programs available for that purpose. That sounds like it might apply in your case.
All that said, I don't know that the state or the feds ever come check on the wage rates paid on our projects (they could, I guess), it's pretty much up to us to enforce the issue with the contractors we award contracts to.
Good luck,
Radar