teiva-boy,
CASO is not needed, and if it's verified with Symantec, someone there didn't know what he was talking about:)
I've verified with Symantec, i've tested in lab and in real environment, CASO is not needed for using Optimized Dedup.
SSO will let you share Dedup storage with other BE servers, that's all you need.
I know that BE Admin guide says this;
"If you use the Central Admin Server Option, you can also copy data from a deduplication storage folder on a managed media server to a deduplication storage folder on another managed media server."
But, you can do same thing without CASO, and information given by Symantec's technical presales is that you dont violate licensing if you do same thing without CASO.
SSO is not only for sharing fiber devices between media servers, you can now use it for sharing Dedup Storage folders as well. Go ahead, test it, find out.
There's plenty of other things you can now do with BE2010, no matter what still open Admin guide says.