coverage under one or more collective bargaining agreements, membership in a labor union, or membership in one or more locals of a national or international labor union. An organization that is part of a plan will not be exempt unless the plan meets certain nondiscrimination requirements. However, if the organization is part of a plan maintained under a collective bargaining agreement between employee representatives and employers, and such plan was the subject of good faith bargaining between such employee representatives and employers, the plan need not meet such nondiscrimination requirements for the organization to qualify as tax exempt