[Symbiote]

That ticket inspector can also turn a blind eye to invalid tickets (apply their own discretion/favours/whatever), while they'll probably need to follow the official policy with an app-based ticket scan.

From the article, it seems unlikely that a data connection is required to validate a ticket, except to prevent the same ticket being shown twice to different inspectors within a short timeframe.

[ilammy]

What stops the inspector from turning a blind eye to app-based tickets?

If you want a true technological dystopia solution then the train car should be engineered in a way that nobody gets in or out of the car without a valid ticket. Like, make entrances a double-door, then you gotta swipe your ticket to board, deboard, go between cars while enroute, etc.

[OJFord]

They definitely need a data connection for a ticket sale, (but they'll go ahead and come back or whatever) I'm not sure about validating digital advance sales.