I have a working copy of DMT tool with the Billion 7800N! Here is a screenshot: If anybody would like a copy, please let me know. NOTE: I can't take credit for this. Somebody made a tweaked version of DMT tool to work with the D-Link DSL-2640B because it wouldn't connect to the DMT tool. I figured: it could be the same problem on the Billion 7800N so I tried the tweaked version and hey, it works!
The DMT Modem-tool really is an excellent analysis program. Sadly it is no longer being developed by Andreas Matthoefer. I think the last version/edition was in 2007 - ironically about the same time as my exchange got ADSLmax. Pity the source code has never been 'open sourced' for others to take up the development. PS early firmware's for the 2640B would connect to the DMT program in its default state, the later firmware releases as you say stopped working with the DMT program.