UPDATE: This issue appears to only be related to a development side of Webex Teams and does not affect the public Webex Teams. In the control Hub users are shown with a SIP address of <userid>@<siteid>.calls.webex.com, but when you enable Webex Calling, for some reason the SIP address changes to <userid>@<siteid>.call.webex.com. The SIP address is apprently what is used by the Expressway Call Connector to generate the remote ID in CallManager. I can not find a way to manually change this, if someone knows how please fill me in.
On production Webex Teams accounts it's like <userid>@<sideID>.ciscospark.com, which apparently does not cause any issues.