I remember smoking was a punishable offence in Indian Railway's trains - but is vaping e-cigarettes legal while travelling in a train in India?
I wouldn't recommend it, especially with the discussions about banning them in the whole of India:
The government, in an ordinance piloted by the Health Ministry, is planning to ban e-cigarettes and vaping devices. A cabinet clearance and subsequent notification would put the ban into effect. The ordinance banning all Electronic Nicotine Delivery System (ENDS) will be brought before the cabinet on Wednesday.
Other news sources include here:
Other discussions on smoking on trains can be viewed here.
Now smoking in train is ban in India.
Not only on the trains, but also on the platforms and even outside the railway station unless you cross to the other side of the street. Better just get used to it. There was a time when smoking was allowed on airplanes and many would light up as soon as the non smoking sign went of