You don't see this very often! A GSP on a rock-solid point being "backed" by a Boston Terrier. I had to laugh out loud.
There's a brush-filled pit not far from the house and on our walk yesterday Emma locked up on a nice point. Mags stopped suddenly and it certainly looked like she was backing her. At least she held her "back" 'til I broke Em off the point. (I don't like her going into the pit and it was probably just a rabbit anyway.)
It's interested (to me at least) about Emma and her points. When she is out by herself she seldom points. She just stalks and busts things out of cover and then chooses whether to chase or not, according to her immediate whim. I've watched her from the house and know this to be true. Once or twice I have seen her lock on a point and when that happens I always go out to her. In those cases it's either a grouse or a pheasant.
But when we are out together she points everything. She's like a little kid "Look at that! Look at that!"
So, if anybody says "You ever see a Boston Terrier backing a bird-dog?" you can answer "Yes, indeed I have!"