Albert - how are things going with your ECO project?
I ran across something today that might be of some help for you. It can be found by googling Franks Chess Page. The link is:
www.amateurschach.de/
One of the downloads is of all the ECO's and he uses the endpoints to run engine vs engine tournaments.
I downloaded a pgn file there and then 'tree'd it' using Chessbase's tree function. I haven't looked at the results much, but it's catching the tranpositions I've checked into.
Interesting stuff, check it out.