I know he will call police if I remove the spikes and poles he is putting in my side yard.

When I told her that I did everything myself she said she knew she was being scammed.She filed a police report and I picked out the couple out of a photo line up that conducted the scam on her because I remembered them coming to tour the house like they wanted to rent it. 

You can set up automatic alerts on the city website for each property for both DNS and police reports; in case there is an issue you hear about it the same day instead of 7 days later when you get a letter from the DNS. 

I'd recommend typing the address into a crime mapping agency (there are several free ones online) and seeing what the police reports are in that area as well as the frequency.

When he returns he may call the police or may not.

The police have been called multiple times by other neighbors (not my tenants).

Can you call the police and have her arrested for trespassing?

A podcast that may interest you is #169 It's how David Greene, a police officer from San Fran, use his ability to work overtime to his advantage.

I guess for me the difference is the area's importance to the city's strategic growth and activeness of policing and security efforts.  

I also like to feel safe during showings and to not have to deal with police calls at my properties.