From the CNIB's perspective, we do not gather information or statistics on this type of information.
As a person who uses a service dog—I know a lot of people who have service dogs—I would say, from the people that I know, I can't think of one guide dog handler who has not faced an incident where their dog has been attacked by another dog. Usually it's quickly handled, but in many incidences the animals have to be retired and they get a new dog. We don't have those stats because it's not reported. For a dog-on-dog attack there's nothing you can do about that. It's two dogs that get into a fight. It's not seen as any different if it's a service dog that's been attacked.
The issue around whether or not someone could, if it was a person attacking...again I go back to if I can't visually identify the person, I can't chase the person, and I can't follow them. Unless I have a witness standing there who stops, calls the police, and identifies them, I have no way of doing anything about it. We don't have any specific statistics.
I know that some folks at The Seeing Eye in New Jersey did a survey of their graduates—and I don't have the stat with me, but I could find it for you—and off the top of my head I believe they said something like 80% of their students expressed that their dogs had been attacked by another animal at some point in time.