LT2 is trainable - you can raise LT2 as % of VO2max. Not sure why you say the jury is out. Older blog post worth reading:
http://www.trainingbible.com/joesblog/2010/03/physiological-fitness-lactate-threshold.html
and another:
http://trainingbible.com/joesblog/2010/03/physiological-fitness-aerobic-capacity.html