With how picky most BPs are I would be surprised if they would just decide one day to try something like that. If that was the case we would be free of all the yippy dogs
I would LOVE to see a BP that could eat a 10-15 pound cat or dog! I have a 5'-6", 3500 gram male that Isn't even close to being able to eat a 10-15 pound animal. Could they KILL something that size...probably. Whether they actually would or not is a different story. I really don't see any BP of that size being aggressive enough to kill a 10-15 pound animal. Most of us have a hard time getting them to eat rats...let alone cats and dogs.
I bring my snake around my cats occasionally and he doesn't seem to mind them at all, no feeding response at all. In fact the cats have more of the issues. So I doubt a bp would even see a cat or dog as prey.