There is a possible way to run train services without NZ Rail being responsible for providing extra services but providing additional income for them.
I would call it Clip On Rail.
A boutique passenger service not providing all the services expected of a conventional rail. This would be achieved by a stand alone company being responsible for organising passengers, ticketing and on board management on the carriage.
It would be no different than a bus with one employee taking charge. A carriage (or carriages) could be hired from NZ Rail or the private company to provide them to conform to normal standards. In other words from the railways point of view it would be simply another freight job! Like taking someone's container on board.
NZ Rail might even set up the company themselves.
No obligation to provide any services either end is the key for NZ Rail, exactly like a bus.
Worth a thought for one of our locals even Bayline?

Pat Dillon, Tauranga.