Environment Waikato conducted a business case study into the feasibility of a rail service between Hamilton and Auckland. We have uploaded it in PDF format here:
Things have moved on a bit from when this study was done. For instance, the study thinks that 1 service a day would be all that is required, but we really think 3 services a day would be extremely well patronised. One business alone, with offices in Hamilton and Auckland, would take at least 10 seats a day on the service.
Of course, having commissioned the study which shows a positive benefit cost ratio, Environment Waikato are now ignoring it completely.