‘The union hired them.’
Or do you mean to say that the union is heavily involved with employment and essentially hires them?
Union contracts can get very constraining for an employer as I understand it.
I don’t know much about union workers and nothing about how it works in NY. In California my brother worked as a roofer out of a union hall. An employer would tell the union hall how many people they needed, union would send them. In other words, an employer didn’t interview, vet employees, the union hall did.