Good question. But the 2006 did throw me.
I found this in BOL:
There are two endpoints available for managing objects on a report server, ReportService2005 and ReportService2006. The ReportService2005 endpoint is used for managing objects on a report server that is configured for native mode. The ReportService2006 endpoint is used for managing objects on a report server that is configured for SharePoint integrated mode.
. . .
The WSDL for the management endpoint can be accessed using the following URL:
http://<Server Name>/ReportServer/ReportService2005.asmx?wsdl
If the report server is configured for SharePoint integrate mode, the WSDL can be accessed using the following URL:
http://<Server Name>/<Site Name>/_vti_bin/ReportServer/ReportService2006.asmx?wsdl
Based on this, it seemed neither of the first two options worked, so I went with the third one by process of elimination.
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