Don’t know about other states but in QLD if we have insurance excesses on the policy if the damage is to common property but only affects one unit (in this case) the owner has to pick up the excess and the insurance pays the balance.
If it is not being done through insurance and the current owner is the one who cut the doggy door surely he is liable for the repair as he did the damage. If it was a previous owner then with what has previously been said on other posts is that responsibility falls to the OC.
I also agree with what Whale says about doors and windows within the lot could be owners responsibility so check the plans (thick line on plan OC, thin lines owner responsibility)