This analogy would only be valid if there were only one store chain in each region. For a better analogy, look at energy distribution, where there are rules that the monopolists have to follow.
Actually, the scenario you describe "one store chain in each reason" is a common scenario. Outside of major urban centers it's not uncommon to have a single grocery store, hardware store, etc.
Energy distribution is different because it's a government granted monopoly.
Energy distribution is different because it's a government granted monopoly.