I hadn't even thought about that. We stayed at BWI last year and the guests in the room next to us had a dog in it. We heard it barking when the returned in the room and saw it walk out on the balcony. We know the staff was aware as the maids were in the hall and also heard it barking when the guests returned to the room, they all turned to look, just like we did, when they all walked in the to the barking dog.
It didn't occur to me at the time that they'd been out with out the dog though at the time I did have my doubts about it being a legit service dog as it was a very small dog that would not be a typical service dog. I'm sure it was possible but I'm going to bet that it was not and knowing now that Disney won't question guests claims regarding animals they want to bring to resorts and or parks I doubt it even more.
I'm guessing that it's going to be just like the
DAS abuse, they'll let the animal situation alone until something bad happens or there are enough complaints that they have to address it.