In the Best Practices whitepaper Analysis Services Processing Best Practices (http://www.microsoft.com/technet/prodtechnol/sql/bestpractice/ssaspbpr.mspx), I had noted in the Troubleshooting Best Practices > Create a system-wide trace file section that you could create a Analysis Services Processing Trace via XMLA. Many thanks again to Dave Wickert for providing this example.
But I had forgot to note where one can get all of the trace event definitions from. To do this, go to the [%Olap Data Folder%]\bin\Resources\1033 folder (by default [%Olap Data Folder%] is C:\Program Files\Microsoft SQL Server\MSSQL.2\Olap) and open up the file tracedefinition90.xml. In there, you can find all of the trace event definitions.