Must admit I don’t like it but I agree with Whale & Jimmy the OC is up for the cost.
You need to get a bylaw registered that states that any alterations to common property are the responsibility of the lot owner (and subsequent lot owners) unless the OC has voted to accept responsibility for the changes.
This won’t help in this case but once registered should provide a solution. This is the sort of general bylaw that SHOULD be written by a lawyer.