In legacy this was achieved through IP for some regional geofencing. In the new model I suppose, PHR's can determine anonymous individuals in their jurisdiction through the following:
Return a list of every business venue or facility in their jurisdiction
Query to see all IDs that have scanned in at these business venues or facilities
These IDs are considered within a PHR's jurisdiction
Acceptance criteria
Scenario: A Public Health Representative signs in and views a list of anonymous individuals