Ideally this government decision should be made within the Budget context. It represents a policy commitment to the project.
It can generally be expected that PPP consortiums will start forming as soon as the policy decision is announced, if not already before. They are likely to commence incurring expenditure from this point onwards.
While obviously the government is able to withdraw from the project anytime up to the signing of the contract, withdrawal for other than transparent 'value for money' reasons will impact on New Zealand's and the government's reputation as a reliable business partner.
The reputational risk increases significantly if any decision to discontinue the PPP process is made after the invitation for Expressions of Interest.
Withdrawal for other than value for money reasons could impact on the likely number of bidders in any subsequent attempt to launch a PPP and, therefore, the cost of the project. For this reason, it is important that the business case has canvassed all issues that are relevant to a decision, including public acceptability of the proposal, so that the risk of any subsequent reversal is minimised.