As far as I know, the pictured Morgan is all Morgan. Sad story connected with this ranch: http://www.allimaxfarm.com/The%20Morgan%20Horses.html
I do know many police forces like to add a bit of draft horse to the mix to make the horses more tireless and/or calm - usually not more than 1/3 although I have read of the odd Percheron being used as a police horse. (I assume the rider has to be pretty large to handle the back width - that would kill me!). I once knew a very mischevious Percheron/Arabian cross named Princess who was aptly named, since she was the alpha horse on the ranch - no stallion present. She was beautiful, but I wouldn't ride her because her back was so wide. (I like my horses tall and skinny.) If you were grooming her, she thought it was hilarious to pin you to the wall of the stall. She wouldn't hurt you, but you couldn't move until she got tired of listening to you squawking to be released. She looked like a knight's horse. A bit like this guy, though IIRC her mane and tail were white: