Your initial speculation about JoeBlow citizen being treated differently than Carrington was unfounded. If you merely Google "Lane County DUII diversion program," you'll find all the answers and more, including the Eugene Municipal Court website with details on diversion programs for other first-time offenses.
From one of the many local attorney websites, there's also this: "A defense attorney is not required to enter the diversion program." The forms are available at the courthouse.