Just for the sake of putting the story of this truck to bed, I did some digging based off of the below photo of the truck when it was first discovered, and I found where I believe the truck was sitting for forty years. It was in Sharon, WI just one block away from the registered address of Sharon Telephone Company shown on the card affixed to the windshield of the truck.
Note some of the building features like the brick work, light poles, and concrete sidewalk. The green bench and the newspaper box are a perfect match.