Here are the steps leading from the dining/cafe area of the MLC Centre leading down to Martin Place.
Until 1971 the site was home to the Australia Hotel, a grand building that billed itself as “The Hotel of the Commonwealth”. It was opened in 1977, one of the many Australian commercial buildings designed by architect Harry Seidler.
I couldn’t find any direct reference or relevance to the blocks themselves. I suspect they are significant to the memory of the Australia Hotel, or the growing influence of Minecraft in modern society.
If only the Sydney CBD had an abundance of free WiFi, we could see more cosmopolitan scenes just like this.