This would be a horizontal integration, as both are banks providing the same service.
It has already been stated in the article that "the combined bank would have greater access to funding and generate savings. The concept of economies of scale can then be brought in, as the combined bank would probably enjoy Administrative and Managerial economies, and rationalisation would also get rid of duplicated services. This would then lead to increased cost savings. Also, it would create a oligopoly market structure in Australia as the combined bank would have 25% of market share, with several large banks like Commonwealth Bank of Australia (worth A$58billion) having the rest of the market share.