"Do the units of dogs have human commanders, who show them the general direction of the ennemy and decide when to set them loose?"

Yes. It's pretty cool.

"Once they attack, can they, unrealistically, still be controlled?"

I don't believe so. The handlers set them lose, and then run back to your lines while the dogs run off and chew on things (ineptly if they are attacking armored wearing troops). Any further orders to the dog unit only applies to the handlers as far as I can tell.