Hi Knightmare,
Suspect you've been asking the wrong questions at the court house. All you need to do is elect to have the matter heard in court if you do not want to pay the fine. You don't file a case. Let the police take you to court if you want to contest the fine.
If they allege the offence occupied on private land, you then raise your defense as being on private land. See my earlier post though, where I suspect the police officer will say he saw you on the road.