Collective Bargaining Does Collective Bargaining Agreements Override Federal Laws

My question involves employment and labor law for the state of: Employer is a federal contractor which means employees work under the McNamara-O'Hara/Service Contract Act. Along with wages, the Act requires employers to make health and welfare payments, or provide "bona fide fringe" benefits. The Act appears to "give" discretion to the employer to either provide these benefits or pay the cash value of the health and welfare benefits. The Act also states "an employee who works 32 hours in a workweek and also receives 8 hours of holiday pay is entitled to the maximum of 40 hours of health and welfare and/or pension payments in that workweek. If the employee works more than 32 hours and also received 8 hours of holiday pay, the employee is still only entitled to the maximum of 40 hours of health and welfare and/or pension payments." The Act states the employee "must be furnished the fringe benefits required by that determination for all hours spent working on that contract up to a maximum of 40 hours per week and 2,080 (i.e., 52 weeks of 40 hours each) per year, as these are the typical number of non-overtime hours of work in a week, and in a year." My question is: Can a collective bargaining agreement (which prohibits the payment of said benefits on holidays and vacations) override federal law stating they must pay it?

Collective Bargaining Does Collective Bargaining Agreements Override Federal Laws