If the construction company has liability insurance it will be interesting to see if the insurance covers actions illegal employees.
I'm sure the insurance policy includes an exclusion for illegal activities. The liability will be on the contractor alone. If he is a small business, the assets likely are balanced by debt. It will come down to how well he has pulled money out of the business and put it into funds that are beyond the plaintiff's reach, such as retirement annuities. That's what the Goldman's could not get from O.J. Simpson.