I have been reading an article about this and have seen it for myself. In my case a friend and I were walking our dogs together, when two of the bitches paused gave each other very meaningful looks and then one when one way and the other in the opposite direction. They performed a perfect ambush on wild pheasant (who was luckily quick enough to fly away) by circling around from different directions.

Has anyone else seen any form of silent communication between their dogs or their dog and another?

Yes, definitely--I was loading two of mine into the car crate the other day (I keep their leads on my wrist normally until I'm ready to shut the door and then I unclip them). One is a confirmed 'hen hunter' and is not to be trusted anywhere near them--he knows how to flush them up from inside the pen and will have them the second they fly out. He must have seen that one of the hens had got out of the pen--did nothing to to tell me (e.g. pull on lead on the way to the car). I got them both in the crate, slipped the leads off my wrist and they both sprang out like literally over my shoulder as I bent down--the hen was dead in seconds.

The little one is not as hunter and has always been letter perfect in getting into the crate--but the older boy let him know there was game to be had. Poor hen.

Ive have this several times with my boys over different things and have thought that it was planned between them that there was no way
they just happened to do it at exactly the same time.

yes,i used to have 2 collies and a little crossbreed who didnt get on that well with kelly,one of the collies.Lady,the cross,would be fast on in an armchair.Kelly would walk past the chair,Lady would get off and Kelly would get in.Time and again that happened,not a word,or a look,even!