I never did. In fact I once got my attorney to threaten filing an anti-trust charge against two other utilities unless they stopped consistent attempts at blocking the utility I was at and a third utility that was using its transmission to keep me from making non-firm power purchases.
The last time power sales were made to California under my authority was in 1987. That is when I left working for a utility and became a consultant to the industry. I have advised folks since then on just about everthing inluding: power plants, transmission contracts, selling power plants, selling/buying utility service territory from another utility, electric retail & wholesale rates, natural gas rates, and a whole much more.
As an engineer, I did something unusual, I took a bunch of business law courses. I especially took a lot of anti-trust law courses. As a power manager, I kept asking attorneys about practices I saw and was shocked by. Electric utilities grew up a regulated monopolies. Most folks I knew in the industry really didn't understand that anti-trust or anti-monopoly laws sometimes applied to them.
The utility industry has had a long history of utilities coorperating with each other to help out during power problems. In a "market" wholesale power system, calling a potential competitor to do anything more than make a straight purchase or sale of some product or service starts to get close to a whole host of anti-trust things that a judge could say were a restraint of trade. I have often felt and told the people I mentored that anti-trust laws were an area they should be especially careful.
In the transition from regulated monopoly to market based wholesale generation, I don't think enough education ocurred on anti-trust laws.
Part of the answer is clear enough: combining in order to prevent a market participant from dealing in the marketplace, as in your example, simply must be unlawful...or we're all in deep sheep.
Anti-trust law as enforced is so amorphous, so subjective, that it's hardly any wonder that large numbers of companies and people aren't very informed about it. I'm not, for certain. When you consider the government's sporadic and highly capricious anti-trust enforcement efforts, though, do you laugh or cry?
They pursue IBM for TEN years, then abandon the prosecution. They allege Microsoft is a 'monopoly', or was that 'an effective monopoly', just at the time Linux is becoming increasingly popular, and in doing so cost private citizens billions of dollars by kicking off the tech-share slide (check the date the anti-trust action was announced...the very first day of the tech crash).
If a (presumably) legal issue can't be resolved through the legal system in 10 years' time, then I say the laws pertaining to that issue are either badly written or thoroughly out of date. Maybe deliberately so, hmm?