I believe you are asking if a cop can write a ticket on private property? If so, the answer is yes. The property is open to the public so a ticket can be written. Also, when you backed up, you caused damage, hence the improper backing charge. Lots of cops write tickets at accidents, that helps the insurance companies determine who pays. As to the pole marker not in the right spot, that is up to the insurance company to determine if it caused the accident, but feel free to use that (with photos) in court.