Since I've been searching for the last hour on Blackberry's support site for documentation on whether Blackberry Enterprise Server 4.1.6 for Exchange will support a SQL 2008 database backend, I figured I would finally post the document that answers the question as well as other combinations of operating systems/server components.
For those of you that don't want to open the PDF, and all of you search engines out there wishing to index my answer so people can actually find the answer in the future:
Installing Blackberry Enterprise Server 4.1.6 on SQL Server 2008 (any edition) is listed as not recommended as the installer apparently won't allow it. Also, installing Blackberry Enterprise Server 4.1.6 on Windows Server 2008 is also listed as not recommended.
Reading into their classifications of supportability, 'Not Recommended' appears to equal 'Not Supported'.