While this article is a bit old, the situation remains
Credit reporting move opposed by big banks
Comprehensive Credit Reporting was "allowed" by the Privacy Act changes last year but remains voluntary. Lots of reasons for people not to participate now, one being that the benefit to a lender is access to everyone's elses data but they dont particularly want to share there own data (because potentially other lenders could go after your customers - despite this being not allowed by the laws). To get over this the industry body (ARCA) draft a set of "Principles of Reciprocity and Data Exchange", this has now been approved by the ACCC and the first major (NAB) has indicated an "intention" to contribute data.
But the other majors arent yet in and the main bureau (Veda) are still opposed to some of the requirements of the Principles. It will happen but its taking a long time!