What is the difference between an MTB position and any other kind of bike? I see cross country racing MTBers with very aggressive positions, with 6" drop between the saddle and bars, and Sunday afternoon leisure riders with their bars set a few inches higher than the bars. The same variation can be seen in my touring club with riders setting up their high quality touring bikes just as they see fit.
Check out the fitting guide at Peter White Cycles, which has less racing bias than most other such guides.