At the end of the day, it is all an economic trade-off. In Maricopa County, where Mesa is located, the City of Mesa has 3 ships (now two going back to three by august), Phoenix has 12 (1 is a twin), Maricopa County Sheriff has 4, Arizona DPS has 4 and all the other cities are talking about getting their own.
So, you take 22 single engine ships in tight budgets and you covert them to twins in acquisition, training and operating costs.
If you look at the total number of accidents/incidents relating to engine failure in the last twenty years resulting in an autorotation, the grand total is one encounter. This one.
If you assume public safety money is fixed, you can cut the ships or hours in the air and do a cost/risk analysis of what happens without a ship in the air. Is an officer shot, do they lose a suspect, is the high speed chase worse? Or, do you cut the number of officers on the ground?
With respect to police air units, the American system has done that analysis and come to the conclusion that factoring in risk versus reward, singles are the way to go.