The T3 website clearly states that the top speed is 12mph unless it's special ordered - possibly meaning a large portion of these things can't top 12mph.

As for bike speed, I don't see why you'd have to hammer it at 25mph just patrolling. I can average 25mph for a half mile or so on flat ground on a 45lb huffy mtb, and I'm not a very strong person. I don't see why such a low speed chase would last any longer than that.