The trick behind a firesale of public assets is to create a false liquidation crisis e.g. by saying NZ is in impossible debt (an 'unsustainable' budget deficit).
The panic this creates, creates the political conditions for public assets to be sold. The outcome of a sale of state owned industrial capital is, like the current liquidation crisis in the wider private sector, for the asset to be sold under valued. The private sector is in crisis because of its indebtedness. Assets sold in the private market are therefore all likely to be undervalued.