As scotlandx advised, if it has been admitted/or is known that the lot owner has caused the damage, simply get the locksmith to come out, install another new compliant lock, and send the bill to the lot owner. They will very soon stop doing things that cost them money.
To be nice, inform them that the locksmith will be called (give a weeks notice) and what will happen if that is still required at that time. In the meantime, have the wire mesh/perspex/etc installed, since it will be required anyway and better to do that prior to the lock replacement (so perhaps the owner will be happier with a single sided keyed lock).
IMHO, it’s always better to negotiate towards a solution, but have a stick ready when required.