There's no inherent discrimination in the changed system
If by this you mean that the system itself is not designed to be discriminatory, then fine, that's probably true. Despite this, I doubt that there is equity in the ability to pay upfront fines between people of different socioeconomic status; in my mind the likelihood of a wealthier person carrying a sufficient amount of cash to pay an upfront fine is greater than the likelihood of a less wealth person doing so, and I think that's logical. I also think it's logical to consider that the individual financial impact of a fine would be greater for a person who is less wealthy, due to assumed lower average capacity to pay the cheaper upfront fine.
I see this system, while not 'rewarding' people who can pay the upfront fine, as being more punishing to those who may not be able to pay immediately, regardless of their personal situation. This doesn't sit well with me.
I've never been issued a fine by the public transport association so I don't know what the previous system was; however, if I were able to make a recommendation it would be to change the stipulation that states that "Where passengers
cannot, or choose not to pay the on the spot penalty fare, the existing infringement process and higher fine applies." to be limited to those
who choose not to pay, thereby allowing those who may not carry such large amounts cash either for personal or socioeconomic reasons to pay the lower fine.
I'm sure that this change in rules is supposed to act as a deterrent just as much as a punitive measure, but I don't think it's fair in its formulation.