Which T&Cs? (A link would have been nice.)
In general, you can't "count" on a BRG absolutely being approved, in any program. So the best approach is to make sure you're doing a reservation that can be cancelled without penalty, and then if the BRG is declined, you can cancel it and book somewhere else (if you don't want the hotel if you can't get a BRG). I'm assuming that (like other programs' BRGs) you don't actually have to book at the other site, just document it?