By accident I already published this article before actually writing this, so it appears in the news feed. Hence the briefest of brief contents:
At http://timezra.blogspot.com/2008/04/oda-ecore-getting-started-guide.html (written by Tim Myer) you will find a very nice description on how to use Ecore Modells as an ODA Datasource, and connect the result to BIRT. I just tested it again using BIRT 2.50 and Eclipse 3.5. Worked like a charm.
I will write more about EMF Queries when I find the time.