See
http://www.y-adagio.com/public/commi...aft_050913.zip for the Xylog XML specs (source format of BBeB books). I haven't seen specs for the binary compiled format, but the mapping is pretty straight-forward.
Edit: actually, here's the link to latest IEC draft (last document on the page) and other related documents:
http://tc100.iec.ch/about/structure/tc100_ta10.htm