Citizen gets the police to pay them for access, then gets the police to advertise the app to them as an alternative to calling non emergency dispatch. In turn more people down Citizen and Citizen can probably monetize that.
In LA they even have Citizen branded patrol vehicles rather than community service officers as a pilot program. So rather than having like an unarmed (and normally unsworn) employee of LAPD in a Prius with a little orange light on the top, you get a private contractor in a citizen branded vehicle doing the patrol.
The big question is if Citizen gets into E911 systems, which have a lot more liability than non emergency type things. Is Citizen going to make a play to become the standard way of contacting 911 via text based communication at some point and attempt to generate revenue via running that infrastructure.