I got a reply (as below) that doesn't really answer the question. Maybe it's more a matter for the Dept or the Attorney General but I'll follow up with NTA for now and see what, if anything, transpires.
Response received:
Case Reference: CA129715
Dear Mr. O'Connell
Thank you for contacting the National Transport Authority (NTA). We refer to your recent correspondence received on 22nd July 2022.
The NTA compliance team will, as always, exercise discretion and common sense in all complaints investigations.
If a passenger card payment problem occurs, such as insufficient funds or the card has expired, for example, drivers should treat the matter in the same way as when dealing with a passenger who finds themselves unable to pay the fare in cash at the end of a journey. A different card may work or the passenger may be able to pay cash for the fare calculated on the taximeter. The passenger may wish to be taken to a cashpoint to get cash to pay the fare or have a third party pay on their behalf. If a passenger refuses to pay and an amicable agreement cannot be found, drivers should consider involving the Garda Síochána. It is an offence under section 24 of the Taxi Regulation Act 2013 for a person who hires a taxi and, without reasonable excuse, does not pay the fare calculated in line the maximum fares order by a verified taximeter.
To assist with local connectivity blackspots, drivers should consider whether the cashless payment terminal chosen includes connectivity via combined connection types, i.e. Wi-Fi, Bluetooth and 2/3/4/5G mobile networks. Explain the situation to the passenger and a practical solution can usually be found. It is particularly useful to explain known issues to the passenger prior to the commencement of a journey.
If there is a significant internet or service supplier/payment processor outage preventing cashless payments for all businesses, drivers must explain this to intending passengers before they get into their taxi and have evidence of this outage to provide to the NTA’s compliance team in the event of a complaint being received. Any such outage is likely to be well publicised and known to passengers.
If you have any further questions, please contact our Information Line on 0818 064 000.
Yours Sincerely
National Transport Authority