Why do the need to build a new power plant? It is only 20 miles long.  Based on your reasoning, New York City has about 200 power plants to power their rail system!  They have hundreds of miles of track with trains that are at least 3 times longer than the planned Honolulu rail and use express and local lines for each route.  The rest of your logic is faulty.  I guess nothing but more gas guzzling autos in 24 hour gridlock is your solution.