Honestly, this has never been an active concern for me, but now I'm worried, too.
We've never actually had any type of plan laid out - I am going to buy one of those decals as soon as I can. I see them taped to windows around the neighborhood, so they shouldn't be hard to find at all. Shouldn't be hard to miss the dog, but it'd be the two cats that I'd feel worried about.
Trent is highly aware of unacknowledged strangers coming in to the house, and always gets free roam when we're out, but I don't foresee any issues with firemen rushing in, in the case of an emergency. He's not one to be manhandled by strangers but when it comes down to it, he has always, always shown a very innate and intuitive trust in people to take care of a dangerous situation. If no one was home and the house was on fire, I'm betting he'd run through the door the moment it was open - he's a dog with a sense of self preservation. I don't think he'd resist to anyone carrying him out, either. At night he sleeps in his crate in the bedroom, and I know he'd be among everyone's first thoughts in a fire and immediately let out.
On the other hand, I worry about the cats. They're easily scared and hide themselves in the smallest and most obscure corners. Sometimes it can even be a task looking for them after we vacuum the house.