The only mounted police I've seen are horseback police in the States, but it seems like they have similar, positive effects, even in urban areas. When they aren't galloping down one of the busy avenues, horseback NYPD are almost always surrounded by people wanting to see the horse up-close. The high vantage point can't hurt either. Even though I still laugh everytime I see a horseback cop waiting at the traffic light and then sprint down the street, it's still a more welcoming site than cops on motorcycles or Segways.

The last day of the California state fair often breaks out into a mild riot...a cop told me that having cops walk directly into the crowd is often enough to break up the disturbances, while not putting the officer or the crowd at great risks...I guess for mischief-level riots (think of kids wanting to go crazy the week before school starts), the crowd might be willing to bang up a police cruiser, but might draw the line at hurting a horse.