The Mazda6s Manual is A65M-R
It is a JATCO tramsmission that shares a great deal in common with the MTX75. How much in common, I'm not 100% sure, but it is a very similar design.
Throw some Redline Synthetic in it and the notchiness goes away.
For more info, you can check out:
http://www.mazda6tech.com (superb site that's growing fast as we learn more and more about the technology in the 6)
and
http://www.mazda6club.com for your regular CEG-like needs.