According BBC more UK train passengers will have the option to use paperless tickets.
From a privacy perspective it is very important you can buy these tickets using cash and without any registration needed. If not, please remember that information being stored not only can but for sure will be hacked.
There is no reason for a public transportation company to know who is traveling, the only thing you have to prove is that your ticket is paid.
In case you say something like I have nothing to hide and therefore accept being registered, please remember that history will repeat. Who could in the 1880’s imagine what would happen in Germany 50 years later. Who could think that it would be life-threatening to say that you were Jewish?
Please remember that privacy and integrity is a human right according UN!