During the 07' season, they have recovered .2 grams per CY using a shaker table. Shaker tables were designed with nuggets and large placer flake recovery. NRG sounds like it is mostly small placer flakes. Small placer doesn't have the size and mass combination to shake down, it is simply passed through the process and put back in the ground.
The centrifuge they are now using will recover a much higher percentage of the around 50% placer what was once being lost. There will be a greater recovery, period. How close to the .4 grams per cubic yard is the question that should be answered today.
From their Website:
During the trial mining and plant commissioning, over 60,000 yd3 of gravel were processed. When NRG shut down the plant in October 2007, 370 ounces of gold had been recovered. This represents a grade of 0.2 g/yd3 recovered, however sampling of the plant tailings indicated that gold recovery was often less than 50% due to insufficient washing and screening and muddy process water.