In my opinion, 2 EOGs will always be required in current scenario. Any of them can power the rake in case of emergency. The actual reason seems to be that the front EOG will be used for supplying the hotel load to coaches, and the rear EOG will be used as Guard Cabin. Front EOG can NEVER be removed, otherwise HOG will not work. Rear EOG can not be removed since guard usually sits in the last coach only. So both EOGs will be required.