I have seen a nice article on how to use the lists webservice from SharePoint 2010 to create a SSRS report:
http://nikspatel.wordpress.com/2010/06/11/step-by-step-consuming-sharepoint-2010-lists-data-in-the-ssrs-2008-r2-reports/
But I don't know if it is also possible with the search.asmx and the queryex method. Overhere is the list of supported data sources of SSRS:
http://msdn.microsoft.com/en-us/library/ms159219(v=sql.105).aspx
Hope this helps
- Dennis