That's my point - seems like private police with both public authority and resources. These officers are directly benefiting churches, private neighborhoods, etc. by providing public services benefitting private institutions.
It's advantageous for police to be present at large gatherings, from a traffic control point of view it prevents accidents with other members of the public that would cost the municipality even more money to respond to.
Also from a security standpoint as people physically fighting or potentially someone looking to do harm with a weapon would both reflect badly on the community and their events, and also require even more of a response.
So if the event organizer is paying for that security from off duty / reserve officers, the community is getting that extra protection essentially for free, whereas they would have had to pay other officers likely for overtime if it wasn't paid for by the event.
Seems sketchy to me.