Sorry for the confusion here. EMPRESS posted elsewhere that LATITUDE fares now use the M fare/booking class and thus will be upgradeable since Ms can be upgraded under current rules.
"And for those wondering, the reason why M won't earn 125% miles anymore is because M will be used for LATITUDE fares instead of FREEDOM effective 01OCT.
"What this means is that LATITUDE fares will become upgradeable if the booking class is 'M'.
Previously, FREEDOM fares used Y and M, according to the May insert we received. This would mean that FREEDOM fare are left with C and Y, which are upgradeable [at least Y is].