I listen to system police on occasion and they are never encrypted on the troop or car to car,the only ones that are encrypted are the ones that are listed as encrypted as Matt04 stated.i don't know if they have the ability to encrypt the troops and Car to car and the east,central and west talk groups.the reason I say that is I was monitoring troop a and the west and east zones back in December of 2012 and I heard the entire communications all day in the clear when the sandy hook shooting was going on, that would be one incident I would think they would of encrypted not knowing if there were other suspects at large,some of the graphic communication I heard ripped my heart out. So I don't know if they can turn on encryption on a particular channel at a moments notice.