Even other fairfield owners can't see BC in RCI---despite the internal system trade preference. I've just never heard it happening.
There are some reasons for this, due to the way FF handles owner deposits to RCI---presently, owners cannot choose what unit to deposit, FF picks the unit for them, and it can be at any resort, not just one the depositor owns. Add to this the fact that BC doesn't really need to book exchanges to sell units. As I understand it, those units are selling so well that the newer towers are being built taller than originally planned!
The hypothesis among the owners on the FF Yahoo group is that FF simply never deposits BC, because it is more valuable to rent unbooked units out directly (which FF is allowed to do at 60-30 days), and the exclusivity works even better than 1-in-4 rules to help them convince folks to buy there.