Benefits and wage supplements.

(a) Any employer who is party to an agreement to pay or provide benefits or wage supplements to any employee shall pay the amount or amounts necessary to provide such benefits or furnish such supplements within 30 days after such payments are required to be made; provided, however, that this section shall not apply to employers subject to Part I of the Interstate Commerce Act [49 U.S.C. § 10101 et seq.]. (b) As used herein, “benefits or wage supplements” means compensation for employment other than wages, including, but not limited to, reimbursement for expenses, health, welfare or retirement benefits, and vacation, separation or holiday pay, but not including disputed amounts of such compensation subject to handling under dispute procedures established by collective bargaining agreements.