The key tax ruling for owners corps is:
https://law.ato.gov.au/atolaw/view.htm?docid=ITR/IT2505/NAT/ATO/00001
It describes when income is mutual or non-mutual, and when non-mutual income is taxed at the corporate rate in the hands of the OC and when the tax liability is divided up among unit owner in proportion to unit entitlements. It is not obvious to me when bank interest would have to be divided up.