This depends on the configuration in the SIP Supplementary Service script. If SUT_UE is specified in the destination, then yes, the entries in the external phone book will be used to dispatch the call. However, if the destination is another Abacus end point, then, the system will grab the entries in the OWN phone book of the specified destination to set up the call. Note that when a proxy is specified in the SUT, the call will be sent to proxy.