A compact fusion reactor a fraction of the size of a fission reactor that produces between one billion to one trillion watts of electricity would have the potential to de-monopolize the energy business. Such a fusion reactor would be cheaper to build, operate and maintain than current fission reactors while producing at least one order of magnitude more electricity. They also have stated that this CFR could be used in conventional power plants, replacing the coal/gas fired heat source with a fusion reactor.

In the U.S., it depends on where you are located. The electric power business has been going through changes, and continues to do so. Here in Florida, at the residential level, we typically get power from a regulated monopoly. There is a move on however, to put a proposed state constitutional amendment on the ballot to change that. Larger customers (e.g. stadiums, municipal utilities, etc.) already can shop around for who to buy power from.

Electric power companies that have been granted a monopoly get regulated as part of the deal. They have to answer to public service/utility commissions (by whatever name) and are limited to how much they can charge above their cost to produce.

There are geographical areas where residential customers can choose who to buy power from, as I understand it.

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Regarding the possibility of fusion powered electricity generation becoming commercially feasible and cheaper than fission powered plants... if it comes to pass, I doubt that the utility companies will be able to gouge the customers on it. Fission plants have been horrendously expensive to build in the later years, which has resulted in public service commissions sometimes agreeing to pass some charges on to customers before the plants were built/operational... in order to make it possible to get lower cost electricity later on. That has not panned out in some cases, leaving a bad taste.
Fusion plants, if they become feasible, should be inherently safer to operate, and cheaper to decommission at the end of life. If a design becomes available that can produce power cheaper than the natural gas fired combined cycle plants... it will be a real game changer.