Which method does the Conductor use to determine the source of an incoming call to...

According to the Cisco documentation1, the Conductor uses the source IP addresses of the incoming calls to determine which subzone they belong to, and then applies the appropriate search rules to route them to the appropriate conference bridge. The conference IP addresses, location IP addresses, and management IP addresses are not used by the Conductor for this purpose. References: 1: Cisco Video Infrastructure Design Guide, Chapter 4: Cisco Conductor, https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/uc_system/design/guides/videodg/vidguide/conductor.html#pgfId-1060629