I was a bit sceptical of that part tbh, so I went to google maps and took a tour of joburg city center. And what do you know? A bunch of the skyscrapers have fences and hoardings at ground level and skybridges connecting them. Things may have improved since then (I'm guessing the building owners have expanded their "territory" to keep the scum out) as I didn't see any piles of refuse or broken sewer mains.