While I can somewhat understand the screw up on the owners part (assuming that your nieghbors aren't peeping tom's), I do think it's not a bad idea to register them with the city police force.
This is a Fredericton By-Law? Do all cities have something similar? I would have no issues registering mine with the local police to avoid this kind of hassle. It also might be a show of good faith on the part of the airsoft community. Show the government that we just want to be able to enjoy our sport at our local fields and show that as a group we are willing to follow the rules and handle ourselves respectfully.
Edit- Apparently from reading above I'm alone in my thoughts on this...