Thanks for the replies. I've figured out that the OAc groups fall off and the reaction does proceed via the mechanism I posted. I read a paper that stated that the reaction mainly occurred through the [Pd]-H pathway, rather than the [Pd]-OMe. Does anyone have any clue as to how the active catalyst ([Pd]-H) is generated? I was thinking that maybe an oxidative addition reaction occurred with methanol at the methyl group C-H bond, but I'm not sure if this is possible.