Unions are warning Wellingtonians to "get used to walking" as they prepare to take action that will bring buses to a standstill.
Drivers and supporters will set up picket lines in Wellington and the Hutt in June and July, to prevent any buses operated by Tranzit from leaving depots in protest over contracts.
It's set to disrupt tens of thousands of commuters, with around 100,000 bus trips taken each week in Wellington.
"We intend to picket them so that nothing operates in this city without there being justice for people who provide public transport in Wellington," Union advocate Graham Clark said.
"Citizens of Wellington, get used to walking."
Mr Clark issued the threat in front of Prime Minister Jacinda Ardern and Wellington mayor Justin Lester at an event at Trades Hall in Wellington last week.
Tranzit was given the major share of bus route contracts previously held by NZ Bus when they were put out to tender by the Greater Wellington Regional Council (GWRC).
Tramways Union secretary Kevin O'Sullivan expected around 240 redundancies at NZ Bus, with drivers having to apply for new jobs at Tranzit and standing to lose up to $200 a week in pay.
Mayor Lester said he has "asked Greater Wellington Regional Council to give it their full attention with Tranzit and the bus drivers to get an equitable outcome".
Prime Minister Jacinda Ardern said "of course we all want to see a resolution, one that's good for drivers and good for Wellingtonians who are commuting and using public transport."
Council of Trade Unions (CTU) President Richard Wagstaff said the unions had advocated for an "orderly transfer" of jobs and conditions for drivers.
But he said there's "no effort being made to look after these drivers in any way" and "a real chance of industrial action when the change-over happens".
Tranzit managing director Paul Snelgrove said over 500 people had applied for about 280 jobs in Wellington, and it had already employed almost 100 people.
He said the company has met with union representatives and the CTU, and its agreements will pay as much or more than those of NZ Bus.
Mr Snelgrove said while workers were free to picket, it would be "disappointing" to commuters.
A GWRC spokesperson said the Council has bus contracts with four companies who operate independently, and it is not involved in negotiating any of their employment agreements.