But a long-term agreement reached in late 2009 after a bitter six-month dispute - which included the suspension of all NZ Bus services during a seven-day lockout of the drivers - is due to expire at the end of this week.
That will make it lawful for either party to take industrial action to press its negotiating position.
The agreement was aimed at ensuring there could be no industrial disruption to NZ Bus services - which account for about 70 per cent of Auckland bus trips and half of all public transport in the region - during last year's Rugby World Cup tournament.
It was reached after the former Auckland Regional Transport Authority withheld $1.1 million in subsidies from the bus company, which came under strong public criticism of its suspension of services during the lockout, forcing many commuters to walk to work.
The authority used some of the withheld money to pay $500 to each of the locked-out drivers, as part compensation for lost wages.
That was on top of a settlement that ultimately lifted their hourly pay by $2, in three stages to $18.75 by February this year.
According to the unions' stopwork meeting notice, the bus company is seeking a further three-year deal in return for an ultimate pay rise of 7.25 per cent, although the first instalment - of 2.3 per cent amounting to 43c - would not be paid until November.
The company has not commented on the negotiations other than to advise passengers to plan their travel carefully on Thursday, and to apologise to them in advance for any inconvenience.
Bus services run by Ritchies, Howick and Eastern, Birkenhead Transport, Urban Express and Airbus will not be affected.