Do free night award certificates work at United States and Canada WorldHotels as well?

Best Western Rewards has a promo where you get a free night award certificate after staying two nights. The terms and condtion state it can be used at any Best Western branded hotel in the United States, Canada, or the Caribbean Islands.
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Its not specific if that just means any BWH Group hotel (WorldHotel, SureStay, or BestWestern) or just Best Western Hotels. If WorldHotel are not elgible, is the BW Premier Collection?

Thanks,