It is my opinion that many organizations that you would consider a "Natural Monopoly" can, by nature, only provide a fair service/cost without being optimized out by the free market.

The two examples provided in the wiki page are not what I'd consider to be concrete:

   - Electricity: Solar Panels will replace these companies when they provide a poor enough, or expensive enough, service
   - Water: Allow people to tap wells on their property. Put them in charge of their own water. You can also run your own septic tank.

Your examples aren't well thought out. Solar panels can't provide electricity at night, so you still need a network (for the time being - hopefully batteries change this sometime soon). Most properties don't have wells, especially in the cities, so you'll always need a functional water network. Networks result in natural monopolies, unless correctly controlled/legislated.

Batteries change this currently. Many people I know have solar installations.

And as for well taps, each building network can tap their own water.