Well, one of the leads that I worked at the trade show seems to have panned out.
Jeff Brown with Beckhoff has sent me a link to an FTP site that has an extremely detailed description of how they implement their ADS protocol over TCP/IP. It is now a publicly published protocol, without restriction for use AFAIK.
If anyone wants to read it, it includes port number, packet layout, command descriptions, etc. Unfortunately it is in the form of a windows help file (ugh). The link is: