With unity connection 9.1 there is now a enhanced message user license that includes ability to configure a standy mailbox at branch office as part of the SRSV deployment.
So to recap there is no separate license for SRSV branch serves. It is configured on a per user bais and licenses are managed by elm. To enable srsv for a branch every user at the branch must have enhanced messaging rather than basic messaging.
Part number for enhanced user
Please let me know if this was helpful by rating the response.
Does CUWL Pro include enhanced message user license? for example, when migrating from CallManager 6.1 + Unity 5.0 to CUWL Pro with CUCM 9.1 + CUC 9, I can't find the option for enhanced message user license.
Enhanced Messaging (Voicemail): The Enhanced Messaging License includes all the capabilities of a Basic Messaging license + Survivable Remote Site Voicemail (SRSV). Enhanced Messaging licenses are included with Cisco Unified Workspace Standard and Professional licenses.