According to this piece at stuff.co.nz the City Council owns the following assets,
Christchurch City Holdings Ltd (CCHL) is the commercial and investment arm of the Christchurch City Council. CCHL manages the ratepayers' investment in these seven fully or partly-owned council-controlled trading organisations: Orion New Zealand Ltd – 89.3 per cent shareholding. Christchurch International Airport Ltd – 75 per cent. Lyttelton Port Company Ltd – 78.9 per cent. Christchurch City Networks Ltd (trading as Enable Networks) – 100 per cent. Red Bus Ltd – 100 per cent. City Care Ltd – 100 per cent. Selwyn Plantation Board Ltd – 39.3 per cent.It's hard to see how any of these assets are in anyway like foreign policy, the police or the armed forces. It is difficult see how non-contractible cost reductions would have negative effects on quality and it seems likely that quality innovations are important in these areas, so (local) government ownership is not justified.