Back in 2000 I did some work for an AOC holder who was conducting operations to "Remote Islands"
Our OM had 15 pages of flight planning data covering every conceivable situation.
One paragraph stated
the pilot in command shall, before commencing descent, obtain the latest actual weather from the Company's agent at the island and, if the weather is below the aircraft landing minima and the forecast does not indicate any improvement in the weather, the pilot in command shall divert to the nominated alternate.
The operation was subject to an Instrument of Approval from CASA and was specific to particular aeroplanes by registration. I cannot remember why the operation was subject to approval by CASA as the CAO does not state approval is required only that the minimum fuel may be subject to direction by CASA. There may have been a requirement in a schedule to the AOC to have approval. Refer to 28BBof the Act.
Posts on this thread have referred to the ASTB involvement. Would not the NZ CAA be the investigating Authority.