If there is no actual collective bargaining agreement (CBA) in place between the union and the company employer, then any arbitration provision in the expired CBA would have no force and effect.The memorandum of understanding (MOU) is not as a matter of law a binding agreement unless the document in and of itself states such.In order to answer your question, you need to carefully read the CBA and the MOU in that such documents control the obligations owed by the employer to the union and vice versa.