Some additional information that seems a bit perplexing to me.

I went back to the white paper you referred to originally.
I copied the autodiscover.xml file off the CAS server to the local computer,
did the registry tweak, shutdown the CAS servers and did the outlook
autodiscover test and it showed the XML for the test file like I expected.
So, the autodiscover.xml file appears to created correctly.
Did some more testing. Removed the autodiscover.xml file off the CAS
server, restarted the server. The outlook autodiscover test still finds the
autodiscover.xml file on the server, even though one does not exist! If I
stop the webservice on the CAS server then it doesn't find it on the server,
so I know it is talking to the right server. I'm guessing there is some
voodoo going on with the scripting created in that directory IIS virtual
directory for autodiscover, because it seems to find a non-existant file and
respond to it. Can someone shed some light as to how it is I'm supposed to
enhance the autodiscover.xml file when physical file has no meaning on the
CAS server?

Thanks.