This is the backward-direction counterpart to ccasLSTClearFwdTimer, setting how long the gateway waits for the clear-backward signal at the MGC's request, again specific to R2 CAS. Because clear-forward and clear-backward come from opposite ends of the call, having independent timers for each lets the gateway apply different tolerance to which side is expected to initiate teardown, rather than using one timer for both directions of call release. On a call being torn down from the called-party side, the gateway relies on this timer rather than ccasLSTClearFwdTimer to bound how long it waits for that direction's release signal.