Multiple employment by members of union
17Where an application for certification is made by a trade union claiming to have as members in good standing a majority of employees in a unit that is appropriate for collective bargaining, and the employees in the unit are employed by two or more employers, or by two or more employers who are members of an employers’ organization, the Board shall not certify the trade union as the bargaining agent of the employees in the unit unless
(a)
all employers of the employees in the unit consent thereto, and
(b)
the Board is satisfied that the trade union might be certified by it under this Act as the bargaining agent of the employees in the unit of each such employer if separate applications for such purpose were made by the trade union.