While I was waiting for Yoast's solution, I tried copying the XML site map to the main site document root. Network good because now Google Webmaster tools shows how many files are in the XML and how many are indexed.
So I thought I'd try the same thing with the one public sub-domain. I copied the XML site map file from the SCO dashboard and FTPed it up to the main document root. Google says it has illegal characters in the file! wordpress/sitemap (1).xml.gz.
I understand that you can feed Google an RSS feed in place of the site map and him investigating it now.