Union president Garry Parsloe said patterns of work among the minority group were still "basically the same" as for his 200-or-so Auckland waterfront members, and shipping lines of Maersk's size did not organise their schedules according to individual port rosters.
In announcing its intention in December 2011 to remove half of its annual schedule of 104 port visits from Auckland to Tauranga, Maersk said industrial unrest had played a part in its decision.
The pay and roster dispute behind a series of strikes and lockouts has still to be resolved, but hopes are building for three days of negotiations next week after the union withdrew its opposition to lifting court orders restricting the port's ability to hire and train staff, in return for assurances that its members would be treated fairly and not be discriminated against in their employment.
Ports of Auckland estimated at the time of Maersk's earlier move to Tauranga that it would lose 82,500 containers worth almost $20 million in annual revenue - about 11 per cent of its overall business.
That was followed by Fonterra's decision to transfer up to $7 million of its business from Auckland to Tauranga.
A port spokeswoman said Maersk's latest decision would result in about 20,000 more containers a year being imported through Auckland on larger vessels, after a switch between the line's Southern Star and Northern Star services on their New Zealand-Southeast Asia runs.
Before last year, both services came through Auckland, while Tauranga handled only the export-dominated Northern Star service.
Port of Tauranga boss Mark Cairns said it was too early to assess what the loss of the Southern Star service would mean for his company.