If I am not mistaken Vern, these were installed back in the mid 1980's when Peterson Avenue was under a major road construction. The medians down the middle of the street, had automatic water irrigation for the flowers and the black boxes house the back flow preventers for the water. I can remember the flowers being watered back then. The water shut offs are in the sidewalk under those round like sewer covers near to each one.
I believe you're right, thanks for the reply. After I read your reply, I realized there are similar boxes on Cumberland around Irving Pk rd. Cumberland has sprinklers in the median. I pass these going to work....