The merger will see the creation of the country's "biggest credit union network", known as CUA, with 75 branches, 800 staff, and some A$5 billion (US$2.74 billion) in assets under management.

Barry Los, CIO of the combined entity, said the ANCU merger is akin to a "convergence project" where data is being migrated from the Fiserv financial application to Abacus on an IBM mainframe.

"It really isn't a software matter, but one of extracting data and uploading it to the Abacus databases," Los said, adding the project is manually intensive because the integration team has to do a data mapping exercise.

It's this manual integration that is resulting in services being the most significant expense for the project, not software.

As to whether improved support for open data formats by software vendors will help alleviate such integration woes in the future, Los was sceptical.