Independent banking experts advising both legal teams in the ANZ exception fees test case met last week to draw the battlelines for the record A$50 million consumer class action.Federal Court trial hearings begin this morning, in Melbourne, into whether ANZ overcharged credit card and bank account customers on late payment fees and dishonour charges in the six-year period up to 2010.Litigation firm Maurice Blackburn initiated the class action, in 2011, on behalf of 38,000 ANZ customers, alleging the bank had used its fee structure to boost its revenue rather than recoup costs.The test case is being watched closely by other banking providers concerned that a victory for the plaintiffs could unleash a wave of consumer claims against the industry.Since launching the ANZ action, Maurice Blackburn has begun proceedings on behalf of another 130,000 customers against the three other major banks, as well as Bankwest, St George and Citibank. The firm's estimate of the aggregate value of its claims against the industry currently stands at around $223 million.Maurice Blackburn's class action principal, Andrew Watson, said he was pleased the case had finally reached the trial stage, which will deal with the facts on costs. An earlier phase of the case (which escalated to the High Court) centred on which ANZ fees could be considered penalties."There will be evidence that emerges in the course of the trial that might be of interest to other banking consumers,'" Watson told Banking Day.Under an order made by Justice Michelle Gordon on November 19, the banking experts advising the legal parties met last week to prepare a report for the court on matters relating to the case.While the matters under discussion were subject to a confidentiality order from the court, they were most likely focused on the methodology used by ANZ to calculate its exception fees, which ranged between $25 and $45 before they were reduced in 2009.Justice Gordon instructed the experts not to confer with the legal teams involved in the case before filing their joint report to the court. The two experts are Will Inglis of Deloitte (for ANZ) and Paul Regan, president of San Francisco-based forensic accountants Hemming Morse (for the plaintiffs).The court directed Inglis and Regan to identify the matters on which they agreed and disagreed, and to give their reasons in the joint report.Maurice Blackburn has used evidence given by Regan to buttress its argument that ANZ's fees were exorbitant and did not reflect the true cost borne by the bank for late payments on credit cards and dishonoured cheques.In 2011, ANZ commissioned the London-based Inglis to prepare a report on the cost structures underpinning the exception fees. His nine-volume submission was presented to the court earlier this year, and, in August, Justice Gordon asked the bank to explain its methodological assumptions.An ANZ spokesman said the bank would not comment on the case before a judgement was made.The hearings are scheduled to run for three weeks.