He said the finite capacity of the region's diesel rail fleet would require even more back-up buses if tournament organisers decided to keep promoting associated activities.
Extra demand had already forced operators to fly spare bus and train drivers from other centres.
The bronze final will be the only remaining match in Auckland to be held on a Friday, a time of greatest challenge for transport, and Dr Warburton said the school holidays would free up more buses then.
Chief operating officer Fergus Gammie said he was "reasonably confident" of being able to cope with a crowd of about 100,000 heading downtown. "But if it goes up to 150,000 there are going to be difficulties."
Opening extra fan zones in Henderson, Albany and Mangere for the finals - which the organisers were considering making larger than planned - would make a big difference.
There was no comment at the meeting about a suggestion from lawyer Chris Moore, who has completed an inquiry for Auckland Transport into the meltdown on September 9, that numbers attending downtown celebrations should be restricted.
Pointing the finger at event organisers for grossly underestimating the numbers, he has proposed entry by free pre-allocated tickets in future.
Auckland Tourism, Events and Economic Development, which estimates 200,000 people descended on the waterfront, despite scepticism from statisticians, would not comment on Mr Moore's suggestions.
Rail operator Veolia has welcomed Mr Moore's report, which appears to have largely cleared it of blame.
"The report takes account of the exceptional circumstances faced on the rail network that day and the serious safety matters we had to deal with," said managing director Graham Sibery.
But Auckland Council member Cameron Brewer described Mr Moore's report and others as "a snow job" and said nobody had yet explained why "very poor guesswork was substituted for some actual forecasting and some modelling of expected numbers".
