NZ Politics

I dunno what train times would look like, but as an example a trip from Wellington to New Plymouth is a bit over 4.5 hours (Google Maps), but an Intercity bus is 9.5 hours. That's over double the time (partly because there's a bit of a wait in the middle, no direct options). I only use this example because I'm familiar with is.

Wellington to Auckland is a little better, with the bus being about 11.5 hours compared to 8 hours of driving, if you get a direct bus.

I'm not really sure what amount of extra time I'm willing to accept to not have to drive. But a bus has to stop lots to pick up and drop off people, and is limited to 90kph max speed. A train can make up for the stops by going faster (rail allowing), and generally doesn't have to slow down for towns that it isn't stopping in, or for traffic or intersections. If you can also get the train to go faster than normal (e.g. higher speed rail) then you could probably make the trip comparable to a car.

Some significant downsides are that rail is expensive to run (pay drivers more, need cabin staff, pay kiwirail for use of rail, have to buy the train which costs more than busses). You can say a train can carry more people than a bus, but that's only helpful if you have the volume of people that makes it true. You typically end up with less services than busses, so there will be less times to suit people so you may also get less people that way. Rail also can only stop where there is a suitable railway station (more money needed), where as you can set your bus routes up to go where people want to be picked up, with many stops not costing more than the cost of a bus stop sign. Many places in the country only have one rail so you now have to plan your routes around other trains (including freight) that busses don't have to think about.

I would be very keen for passenger rail, but I can't claim I'm gonna use it enough to cover the costs of running it.

I do wonder if there would be potential in high-speeding existing commuter trains. The one that comes to mind is Hamilton-Auckland. If we can half the time you'd probably more than double patronage, and that would be a lot shorter distance (and so more feasible) than many other other ones talked about in this post.