The fenceing acts is the same throughout Oz as far as I know.
SUMMARY FOR FENCES
- A boundary fence between a lot and an adjoining property is shared equally between the body corporate and the adjoining property owner.
- A dividing fence between two lots is shared equally between the lot owners.
- A dividing fence between a lot and the common property is shared equally between the owner of the lot and the body corporate.
This is the legal rule but as Whale says you can come to whatever arrangement you like agreeable to all parties.