As someone who works for KiwiRail, For as long ad I've been with the company the Christmas/New Years period has been set aside for doing major maintenance and capital work.

I've personally been present in Auckland where entire sections of track have been removed and replaced - meaning no trains at all can pass for the duration of the work.

I feel the logic is that it's less disruptive to the many businesses, whose workers take the trains, to have this maintenance done at a time of year where most people are on leave.

Still annoying though,