I've only worked with dogs in a simpler setting (Wizard of Oz, one dog, in highschool). But what the owner/trainer emphasized and proved to be key for us was to be sure to have the dog bond to the actors who interacted with it. Having the dog get to know them (in our case Dorothy and the Travelling Salesman, as Toto was played by a human actor in Oz), and spend a good amount of time with them made the dog want to go to Dorothy when released. The owner was also sure to have the dog practice taking commands from its 'scene partners' extensively, again so it would look toward them for direction. Basically, we had the dog in rehearsal several times a week to get to know the company and bond with Dorothy. Of course, our dog belongs to a woman whose two passions in life were breeding Cairn terriers and training them to play Toto, and had the time to attend rehearsals.
On the treats note, be sure to ask the owners how the dogs will react to the treat of choice; something meaty is always a favorite but it makes some dogs gassy. Our Toto got really gassy every night after the hotdog stealing scene.