Hi Craig,
AFAIK, there is no dependency on Exchange / Domain Servers for installation of Yukon. They work the same way they used to work earlier. The functionality of publishing a SQL Server to AD still exists as it used to exist in SQL Server 2000. The exchange server still hold its own data store. I think I have answered your question here.
Vinod Kumar (MVP-SQL Server)
http://www.ExtremeExperts.com