For months, supporters and opponents of BellSouth Corp.’s planned merger with AT&T Inc. have been preparing to convince the Georgia Public Service Commission that the marriage will or will not hurt competition. But much of the oral argument at Tuesday’s PSC hearing is expected to focus on whether the PSC even has a say on the merger.

In joint comments filed with the PSC, BellSouth and AT&T contend that the facts “should lead the Commission to conclude that it does not have authority to review this merger.”