Railways Act, 1989
27. Use of rolling stock.
A railway administration may use such rolling stock as it may consider necessary for the construction, operation and working of a railway:
Provided that before using any rolling stock of a design or type different from that already running on any section of the railway, the, previous sanction of the Central Government shall be obtained for such use.
Provided further that before giving any such sanction, the Central Government shall obtain a report from the Commissioner that he has made a careful inspection of the rolling stock and, in his opinion, such rolling stock can be used.