Following may happen to Diesel locos after majority of BG is electrified:
(1) We shall be seeing some diesel locos operating for several years in electrified IR network as we see today.
(2) Some diesel engines still have to be maintained by IR for use in emergency, power/OHE failure, accident etc
(3)Diesel engines can be sold/leased out to neighbouring countries which are having BG...
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(4) some of the isolated branch lines which are not a part of long route may not be electrified and continue with diesel traction.
(5) IR may try to retrofit the diesel locos with e-loco eqpt