Question in the title...can you?
I played some games with a friend and will buy the core set from another friend tomorrow. Probable gonna grab Mediterraneans + the dester/winter board expansions...and eventually the xpac that features the Russains.
Are those scenarios playable on the oversized boards?
Not really. The base game scenarios are set up for a smaller board. You would have to do some heavy modification to transfer it over. Stretch it out I guess.