I am a Bike Patrol Cop, and am also our dept's maintainance officer. I have been to an IPMBA (International Police Mt.Bike Asso.) week long conference. We use Trek police bikes, and generally the Trek is thought of as the best package out. I'd say they make up probably 60% of the police market. The Fuji's and S&W bikes are crap. The Cannondale is a nice package and it appears they are really looking to secure more of the market. I would never consider it because of the Head Shock. My personal experience with it is not good and Cannondale will not make any of the tools to service it available to the general public, so it makes you a slave to the dealer.
As far as a single speed mt.bike is concerned, not a chance. I need and use all the gears. From going through festivals and bar areas at less then walking speed, to hammering at max speed to an emergence call. As nice as it would be to have a Brooks seat, the bikes are shared with other officers and they are expensive. We replace a third of the seats every season because of rips, bent rails... Much easier to justify to the boss a $25 seat them a $100 seat. The bikes take a real beating and need far more maintainance per mile then someones personal bike. We only have 10 bike officers and it seems like one or 2 bikes are always out of service for something.
Paul B