Thanks for your input Jay and Brad.
Brad: Some limited reading this afternoon suggests that the basic compound joinery techniques required for hip and valley framing were in use by most European carpenters, but it's possible that the curved timber techniques were unique to the French. The UNESCO application doesn't reveal anything unique other than the continued oral education of trait which still forms a part of the modern carpentry diplomas, where such traditions have perhaps been lost in other cultures. (I know that Tedd Benson admires the French compagnonnage).
Jay: I've downloaded Lassen's thesis, although he seems to be more concerned with the actual approach to using a plumb line (which formed the basis of another paper of his that I have), than with the layout techniques used to position the timbers in the first place.
To be fair to them, most of the carpenters here with whom I've discussed trait are aware of the long standing timber frame cultures in Asia, and the most close minded comment I've heard yet came from an apprentice architect who was rapidly corrected by his carpenter peers when he said "but French carpenters are the best in the world aren't they?".
With regard to the beauty of trait, I still remember the moment when I learned to produce the "engueulement d'aretier" (the cut at the top of a hip / valley rafter where it meets the post, or ridge beam) using the "sauterelle" technique. Rather than producing the actual cut plane on the floor and tracing that up onto the timber, you find the angles which can be reproduced onto the timber using a bevel gauge. After tracing some long lines on the floor (without necessarily understanding why), the angles appeared and I duly traced them onto my timber. I cut the joint and for the first time since starting my diploma, when I presented the timber the joint mated perfectly first time. It felt like magic. Interestingly the compagnons are often trained with a heavy emphasis on the sauterelle which makes their trait more complicated relative to the simple subjects for the first level diploma exam and results in them often being a little more pushed for time! That said, once you've mastered it, the advantage is being able to work from a scale drawing with just the timber lengths and the angles, and not needing to keep moving timbers around.
Do you have any good starting references for the Asian layout systems. While I'll probably not get my head around them in time for my little talk, I'm still very interested.
