I believe a better comparison would be Comcast also having a Netflix competitor… let's call it Xfinity Stream. And then they make Netflix have extra costs (say, having plans that have low monthly bandwidth caps that limit how much you would be able to use Netflix) but exclude their own service from having those costs. Essentially, making an artificial floor on competitor prices where their own service can ignore that floor.

… Let's just say there's a reason my example is oddly concrete.

In your example, as far as I know consumers do not actually interact with the power plants, and have no choice on what utility company to use; to do so would require duplicate infrastructure. In the (either) app store case there is — I can still install the Microsoft mail client instead of the Apple or Google ones.