NZ Bus executive Tonia Haskell said it looked forward to "a constructive conversation that results in positive outcomes for all parties".
But Rudd Hughes of First Union said drivers were upset about new rosters introduced several months before their collective employment agreement came up for renewal six weeks ago. "They want to get back to the bargaining table as soon as possible," he said.
Auckland Tramways Union president Gary Froggatt said potential industrial action approved by the drivers ranged from working to rule to a full withdrawal of labour.
NZ Bus refused a request to keep paying those who attended the stopwork meeting, after failing to reach agreement with the unions on rostering enough drivers to maintain normal services.
Although most buses were off the road from 11am yesterday, normal operations resumed at 3pm.
Mr Froggatt said although a militant group wanted to stay out, most drivers accept an obligation to the public to get back for evening commuter services. "Our philosophy is that if we take them to work in the morning, we should take them home in the evening."
But he said the unions gained a strong mandate to take whatever action may be needed should a return to talks not yield a better pay offer.
NZ Bus has offered a 0.75 per cent or 15c increase on an hourly rate of $20.40c for drivers with more than nine months' service, against the unions' claim for 2.95 per cent.
Mr Froggatt said existing pay made it difficult for drivers to afford Auckland's rent rises.
The unions are also trying to roll back the roster changes, under which most drivers work rotating shifts.
"It's unacceptable, and we are going to fight to the bitter end over the rosters," Mr Froggatt said.
Mr Hughes also served a strike notice on Birkenhead Transport on Monday, but withdrew it after the firm agreed not to ditch overtime pay.
But he remains in negotiations with three other city bus operators, and says he is concerned about a non-unionised provincial company keen to win business in Auckland.
He called on Auckland Transport to put a higher premium on quality, fearing "a race to the lowest wage".
Opposing sides
Drivers and service staff involved in the dispute - about 1000.
Main differences:
• Pay: Company offering a 0.75 per cent rise; unions want 2.95 per cent.
• Working hours: Company rostering about 80 per cent of drivers on rotating shifts; unions want that down to 40 per cent.