Attendant Control of Trunk Group Access does not work with an SBS Trunk Group.

Centralized Attendant Service (CAS) does not work over SBS trunks, since CAS requires release link trunks (RLT). However, you can use CAS to direct an incoming SBS call to a centralized attendant over an RLT. Likewise, a centralized attendant can extend a call over an RLT, that the system then routes to an SBS trunk.