In Trading Systems That Work by Stridsman, there are a few chapters on optimising a mechanical MA system with TradeStation. Yes, I reckon you can get profit from it, and if sitting around while your computer trades for you for mediocre profits are for you then fine. So I say YES it's possible to get an edge. The trouble however is that you must optimise the system every now and then ( more backtesting) to find the correct MA's as markets change as we all know.
The advantage of the discretionary trader is that he sees the move well before the crossover, and can also determine whether to take the trade or not (are we trending or not). I believe this is far more profitable.