What evidence would you have that the signs weren't there earlier?

The paperwork that showed the work order for placing the signs.

So you're going to spend more than the cost of the ticket on lawyers, repeat court appearances, and subpoenas?

yep, and call the local TV station - they love these type of filler stories that make cities look like crooks

Good luck with that

well we are Europeans and were on the vacation. dealing with court and police is the last thing you want to do on your holiday