The Central Government may, by notified order, direct that all or any of the power exercisable by it under this Act, except the powers given to it under section 3 to apply the provisions of this Act to any railway company or the powers given to it under section 12 or section 18, may be exercised by any State Government, and where any powers are so delegated, they shall be exercised subject to such directions as the Central Government may issue from time to time.