I agree, this is a real 5.1 mix. So there never actually was a 4.0 mix, i guess?
Compared to the HD-DVD all channels have different sound information (levels/dynamic range is different, the LFE is virtually silent on the HD-DVD here, rears are quiete different):
DTS Cinema:
http://s1.directupload.net/images/130830/bcaqn5ic.png
DD+ HD-DVD: