In terms of the cost, for systems that aren't heavily used (but nonetheless are essential) getting rid of the fare would probably actually save money, because the slowdown in service, the confusion over payment, and the whole infrastructure to support and enforce payment is actually more expensive than the revenue it generates. It would also serve the population better, be a more pleasant and relaxing experience for riders and drivers, and speed up service. So even if it doesn't increase ridership, it's still worth doing.
A bus from where I live to London takes about 5.5 hours, compared to 2 hours on a train. I can also get a meal served on a train and work comfortably at a large table, which I can't do a bus. Busses definitely don't always win over trains. I think they hardly ever do.
And London has the best bus system in the UK
Interesting. So making it free actually increased costs.
For longer journeys, buses are far too slow. When buses replace trains (e.g. for track maintenance) in Melbourne, travel time usually doubles.
It really comes down to, does it go where you want from where you want when you want and all this on a timely basis. Hence the big reason buses always win over rail as they can adapt to changing needs.
[1] https://www.theatlantic.com/business/archive/2015/01/why-can...