Still looking for those OIDs (running IOS 15.2(1)SY2, if that matters)...
Also, I think the "Fabric connection" section here is wrong:
http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst6800/hardware/installation/guide/b_c6800_modules/b_c6800_modules_chapter_01.html#concept_1CAF116561484CCEBDB1434271D98687
I believe fabric channel 0 includes ports 2,4,...,16, channel 1 = ports 18,20,...,32, channel 2 = ports 1,3,...,15 and channel 3 = ports 17,19,...,31.