I had thought that, but probably too early in the morning for that (7.30-ish) - looks to me like people/dogs have been sleeping in the cars and without putting too fine a point on it I don't think you'd be giving these guys your pedigree dog...
At this precise moment I'd give both my labradors, my spaniel AND her five pups to anyone who would take them, the entire bloody lot have got the farts.......
Professional dog-walkers for the chattering classes would be the most likely explanation.