SAB is designated as a pool in the official disclosure documents as for BCV use. As a result, legally, there are only two ways SAB use can be taken away from BCV owners -- the pool is closed for use to all (YC/BC/BCV) such as by a decision to build a new one or rebuild that one (or just temporarily during refurbishment), or 60% of the BCV owners vote to take away their right to use SAB (I am pretty sure that is not a vote that would be easily got).