Any reader in the ACT, check s.23 of the Unit Titles (Management) Act. Subject to a set of conditions in that section, the OC can do all that is required to install sustainability infrastructure on the common property with one ordinary resolution. Also, the Act now makes it clear that the Sinking Fund Plan can anticipate expenditure on infrastructure improvements, not just strictly maintenance.
We used this section to install a PV systems a few years ago. It is working just fine, as expected.