If you think it's crazy for this lone lawyer to have gone through this crusade, keep in mind that Indian Railways fought in a 100 hearings for ~25 cents, and their lawyers don't work for free. How bonkers is that?
The plaintiff may not have incurred any legal costs, but the railway certainly cost the court a lot of money over the years.
If they are suddenly on hook for refunds in a way they weren't before, there's a loss of potential future revenue and the additional cost of refund issuance bureaucracy. In a country the size of india even a 0.1% overcharge rate could add up to significant money. I can see why they would want to limit customers to disputing prices at the time of ticket issue.
It's not hard to find examples of private companies litigating over matters that seem superficially petty.
It’s a joke. Always has been, from the colonial times.