/usr/local/frontpage/ contains a configuration file for every domain on which FrontPage extensions are installed. There will actually be two files for each domain, one for port 80 (non-SSL) and one for port 443 (non-SSL), in that directory. You could create a script to take a directory listing, parse the domains, and use /usr/local/cpanel/scripts/whoowns to get the account that owns each domain.