The greatest unknown is the marginal benefit of the exercise. Unfortunately the Auckland Council and related bodies have tapdanced around this important topic.
For example, in the Auckland Council and Auckland Transport document "Response to the Minister of Transport (July 2011) Statements regarding the City Rail Link", the only statements on the topic of increased passenger patronage or specific benefits were statistics and projections regarding the previous $1.14 billion rail electrification project.
The inference being that patronage and public benefit increase if substantial capital works occurs - the Field of Dreams approach, if you build it they will come.
That report further ducked the matter by framing the patronage statistics in terms of "rail boardings," ie one-way trips, rather than on the number of unique users.
Thus, the report stated that the number of rail boardings was 10.4 million in 2011. Assuming that all riders make daily round-trip travel in a conservative 240-day year, that implies approximately 21,700 commuters rode the trains three years ago.
The October 2014 Auckland Transport "Transport Indicators Report" stated "rail boardings" as approximately 11.5 million, which translates into 24,000 people riding the trains every day on average.
The 2011 report projected that 2014 figures would be 14 million rail boardings or 29,200 daily passengers.
Regardless of that failed projection, if an additional 5200 people rode the trains daily, it is still difficult to justify a $1.14 billion multi-year project. Even more so given actual marginal ridership increased by 2300 people.
Unfortunately, the fallacy of comparing Auckland to Brisbane and Perth persists. This seems to be done solely based on similar population statistics. Those Australian cities' dramatically increased train patronage levels coincided with lengthy and deep economic prosperity unlikely to occur here.
Assuming the Auckland Council is rational, it will try to fund its half of the project for as long as possible at a fixed rate to mitigate risk. If so the council might be able to fund itself at around 6 per cent for 30 years. This means annual interest on the debt of about $7287 million.
Unfortunately, the current council is not in a position to engender much public trust. Since the creation of the new Auckland, municipality taxes have increased at a faster rate than before, city services and amenities have decreased, and the administration has done little to show fiscal responsibility. It is difficult to trust city officials to manage a project of the scale and expense of the CRL given their past and current performance.
Given the extraordinary costs and uncertain benefits of the current rail link and the accompanying Auckland city centre masterplan, a better solution may be a simpler one - create expanded business zones near where people live instead of trying to bring them to the CBD from their suburban homes.
Given the duration and scale of the CRL, it is important for Auckland residents to have full disclosure of the facts and alternatives. Indeed, it may be that the 2016 municipal election will then effectively be a referendum on this project.
The "Field of Dreams" approach failed with the $1.14 billion electrification project. There is little reason to believe the CRL will be any more successful, just more expensive.
• Loren Portnow is a University of Auckland law school graduate with an interest in promoting transparency and accountability in government.