I don't know about growing organic potatoes in plastic bags. There is some evidence that rubber and plastics leach chemicals into soil. Hoses, made of PVC (though it is not well known in the US) leach lead, especially if they lie out in the sun.
Since potatoes need full sun to grow, those bags are going to get pretty hot. Before I used this method, I'd like to see some testing to make sure that plastic bags are safe for growing food.