The intention is to identify possible visa and welfare frauds by comparing records of partner visa applicants (and their Australian sponsors) and Centrelink customers who claim that they are single. It is expected that both departments will be investigating from either end and providing suitable remedies if there is not a valid explanation.
This is not the first case of government departments sharing data. The DIBP and the Australian Tax Office (ATO) sometimes share information, in particular when it comes to employer sponsored visas and compulsory payments, or lack thereof, of superannuation. When discrepancies are found the DIBP would refer the sponsor directly to the ATO.
It is safe to assume that the DIBP will cosy up to other government departments where appropriate, now and into the future, to ensure the integrity of the migration programme.