Sydney is still being influenced by overseas trends right now as trams become popular again across large western cities. So do they actually make rational decisions or just follow whatever anyone is doing at the time?
I don't see either line making a financial return on the investment, but the NZ government is financing it all by plundering the NZ Super Fund, which was originally intended to provide super payments for NZ's over-65-yr-old retirees. Of course, they're framing it all as "the Fund is making a long-term investment in the country's transport infrastructure", making the eventual huge losses some other goverment's problem.