Looks like someone did manage to rip the broadcast master - http://batman-news.com/2017/08/16/batman-v-superman-imax-footage-leaks-online-in-hd/
EDIT: ok - basically back at the start of July a group of Russians did exactly what I planned to do here, only they managed to get the broadcast master of the extended cut (not theatrical) from the ivi.ru VOD service. So all that remains is - someone would need to go through the IMAX footage and clean it up accordingly, overlay the 2.40 crop if necessary…like people did on the SW TFA IMAX scene.
we need a copy of that 😄