I think that the question is... If a person wants to gain muscle, without gaining fat, what is the best way to do it? To gain muscle quickly, one probably has to maintain a calorie surplus. That surplus with high-ish carbs does build muscle, but it also seems to put on fat.
Perhaps the calorie surplus on a LC diet would result in muscle gain without the fat.
This study suggests that it might be possible, but does not directly answer the question. The LC eaters gained 2 lbs M. and lost 7 lbs F., resulting in a net loss of 5 lbs. In other words they did not eat enough calories to answer my question. If they would have eaten enough calories from protein and fat, that they did not lose any fat... how much muscle would they have gained?? And how would that compare to a higher carb diet at the same calorie level?

I agree that eating higher carbs 'seems' to be good for muscle growth... but there are other factors to consider. The carbs increase muscle volume because of glycogen and it's ability to hold water in the muscle. This looks good but does not represent actual muscle fiber growth. Anyone could achieve this state temporarily by binging on carbs for a few days.

I would like to see more studies about the 'best' diet for muscle growth while keeping calories high enough that fat loss does not occur.