Fine. As I understand it, when a third party represents the federal government, it must respect all of the laws of the federal government. One of the laws you must respect is the Official Languages Act, just as all departments must. You deal with subcontractors for sponsorships, advertisings and other matters, because that it how promotional work is done. The objective is also to ensure maximum efficiency.
Under their contracts, do subcontractors face the same requirements as you, namely to ensure that everything is in both languages?