TFL cannot prevent business owners (Taxi Drivers) from using equipment they already own so the equipment they are forcing into vehicles will eventually become redundant.
All the suppliers of this equipment know this very well, and it will be seen as a duplication of process and go down the same route as the mandated issues of emission abatement fittings and receipt printers..... straight into the dustbin of TFL ineptitude.
The costly route of 'free' fitting this equipment is bound to be clawed back eventually by the complicit companies creating a monthly levy charge which will be introduced as soon large enough numbers have been fitted and as projected profit costing and failings becomes patently clear to them and this will allow the drivers the complete opportunity to bring this un-welcomed TFL intervention to an unceremonious end.
If your Card processing company issues minimum "low usage fees" which may be linked to their own projected monthly fees AFTER you sign for free fitting and non usage quota linked usage basis you will undoubtedly have an immediate cost free contractual exit and cancellation due to a serious financial material fact alteration, so read your contract carefully before signing or ask what will happen if they suddenly introduce monthly fees to cover low usage cost because it will happen.
What will that mean to the TFL mandate who will try to coerce you to pay up by threatening to remove your plate because you no longer have rear card processing usage facilities?
TFL could never win that argument legally without examining the suppliers contract so the mandate would die just as the previous ones have.
greenbadgejohn (on twitter)