Hi John,
I havent tried multisite with CCA 2.1 yet to see the Multisite manager in action but plan to after SMB Nation show this weekend.
But I did build some multisite collateral in the last releases, which I think answers your questions.
https://www.myciscocommunity.com/docs/DOC-1809
In particular, the difference between page 4 and 5 is multisite is connected using SIP and then shown using H323, respectively. You will want to use H323 for intersite connections so video can be used (CUVA).
There is also a doc on the community that has thhose ppt pictures in an At A Glance doc and a full blown applcation note showing how to build 5 sites in a multisite, which BTW is why you need a steering digit and a site index. I suppose if you had just 2 sites, a single unambigious digit might be used, but I havent tried that since we support up to 5, so we design for that way.
https://www.myciscocommunity.com/docs/DOC-1432
Hope it helps
Steve