Railway staff records created in India before 1947 remain in India, as do the records of railways built, owned or operated by the Indian Princely States. The records that survive today in the India Office Records and other collections held at the British Library (and elsewhere) do so mainly because they were originally created in the UK.
Categorisation of trades and occupations by staff types
The National Archives at Kew hold many different types of railway staff records but none relating to the railways of India. However, Appendix 2 of its Research Guide, Railways: Staff Records, categorises many different railway trades and occupations by staff type and can be consulted here.
Knowing your ancestor's staff type will be useful when consulting railway staff lists and registers.
India Office Records, "Railway Employment", Help for Researchers.