I guess the reason for this is that for each and every time officers have to run to Delhi for any new decision or work. We all know how "fast' our bureaucracy works. With the ambitious plan to revive the age old Mumbai suburban network time plays an important factor.
Also Sir, Suresh Prabhu is a different man. Unlike previous RM's he not a person who will only work for vote bank. I can bet, he will not "ignore" other zones,what other members are accusing him. That's why Modi has selected him. He has never been accused of biasedness n his whole career.