When sharing a calendar with another user the calendar can be found either as bound resource or via calendar-proxy-(read|write)-for.

If I understand http://tools.ietf.org/html/rfc5842#section-3.1 correctly, the property DAV:resource-id is to identify if the two resources are the same.

I've shared sogo1's calendar 'Public' with sogo2. Using the credentials of sogo2 it's accessible via /SOGo/dav/sogo1/Calendar/217D-52127080-19-613AAD00/ and /SOGo/dav/sogo2/Calendar/sogo1_217D-52127080-19-613AAD00/

If I send this request to both calendars:

<?xml version="1.0" encoding="UTF-8"?>
<A:propfind xmlns:A="DAV:">
<A:prop>
<A:resource-id />
<A:displayname />
</A:prop>
</A:propfind>

with "depth:0" I get:

<?xml version="1.0" encoding="utf-8"?>
<D:multistatus xmlns:D="DAV:">
<D:response>
<D:href>/SOGo/dav/sogo1/Calendar/217D-52127080-19-613AAD00/</D:href>
<D:propstat>
<D:status>HTTP/1.1 200 OK</D:status>
<D:prop>
<D:resource-id>urn:uuid:sogo1:calendars:217D-52127080-19-613AAD00</D:resource-id>
<D:displayname>Public (John Doe <sogo1@sogo-demo.inverse.ca>)</D:displayname>
</D:prop>
</D:propstat>
</D:response>
</D:multistatus>

and

<?xml version="1.0" encoding="utf-8"?>
<D:multistatus xmlns:D="DAV:">
<D:response>
<D:href>/SOGo/dav/sogo2/Calendar/sogo1_217D-52127080-19-613AAD00/</D:href>
<D:propstat>
<D:status>HTTP/1.1 200 OK</D:status>
<D:prop>
<D:resource-id>urn:uuid:sogo1:calendars:sogo1_217D-52127080-19-613AAD00</D:resource-id>
<D:displayname>Public (John Doe <sogo1@sogo-demo.inverse.ca>)</D:displayname>
</D:prop>
</D:propstat>
</D:response>
</D:multistatus>

Since the resource-id doesn't equal ("urn:uuid:sogo1:calendars:217D-52127080-19-613AAD00" vs. "urn:uuid:sogo1:calendars:sogo1_217D-52127080-19-613AAD00") there is no way to tell for a client that both calendars are the same, or did I miss something?