 As can be seen from this table, there has been minimal increase over 5 years – public transport mode % of total trip legs by region (from NZ Household Travel Survey) –

More up to date figures are available for numbers of bus passengers, which show declines in most areas outside the main cities -
Buses are the most common form of public transport in New Zealand, making up the majority of trips in every city that has public transport (and often being the only public transport mode available).InterCity and SKIP Bus are the only companies operating city to city bus transportations.They are followed by trains, which are found in Wellington and Auckland.