In some states it depends if the unapproved work is a service or not.
In Victoria, an owner is responsible for a service from where it exclusively serves the owner’s lot only.
For for example, a split system air conditioner or a TV antenna that serves only one lot would always be the lot owner’s responsibility to repair/maintain/replace. As would any damage to common property that the service causes.
An unapproved common property building alteration is another matter. The OC is always responsible for common property maintenance and repair, including altered common property, unless an exclusive use arrangement has been made. But an OC can always try to reinstate any unapproved common property alteration and try to recover the costs of doing so.
I can’t see how an OC can force a current owner to reinstate a common property alteration that the current owner did not do. And VCAT seems to agree. Here is a case where a deck was built without OC permission by a previous owner.