I understand the ARC's report, is really intended to be recommendations to the Australian government, not recommendations to the various institutions that were investigated.
The ARC was implemented to investigate how large a problem child abuse is within institutions. True, the ARC cannot implement laws and ensure enforcement, but it had authority to report cases which it learned about. The problem within Australia was found to be so prevalent, the ARC needed to be extended to 5 years. The commission's final responsibility is to provide recommendations to government (law makers) on how these problems can be prevented or at least be reduced, and what should occur when there is suspicion or an allegation of child abuse.
With the ARC submitting its report to government, it then is the government's hands to review the data and to hopefully adopt or better the recommendations so that new requirements and laws are enacted.