So how has the economic organization of the River running oligopoly fared since I summarized it in 2003?* Tightened a bit, I would say.
To summarize the background, (and see the pages from my book below), the events of the 1970's climaxed as a result of the 1980 election that brought the Reagan administration into power, including the motorized commercial operators' (comm ops) legal champion, James Watt, as Secretary of the Interior. At the same time, the Republicans gained a majority in the Senate, empowering the pro-comm op Senators, Barry Goldwater of Arizona and Orrin Hatch of Utah. This capped a dozen years of struggle over river traffic management as the National Park Service and Grand Canyon advocates 1. tried to get a motorless Grand Canyon Wilderness established, and 2. tried to develop & implement a research-based, environmentally sound, experience-enhancing Colorado River Management Plan (CRMP). The struggle resulted from the resistance of the comm ops, particularly those using large motor-driven rafts.
The effect of the 1980 election was a political de-railing of both the Wilderness and the CRMP, marked by the passage of the infamous Hatch amendment. This political "settlement" of the main issues was locked into place by a comm op-friendly CRMP revision developed and then administered by new Grand Canyon National Park Superintendent R. Marks, who not only lasted through the 1980's, but presided over a further CRMP updating (solidification) at the end of that decade.