Jacket potatoes in Australia are whole potatoes normally cooked in the oven or thrown into a weber, crisp on the outside, cut in halves or a cross made in the top and squeezed to make it sort of pop open. It is then topped with butter or sour cream or all sorts of things to make a complete meal or potato removed and mixed with other ingredients, piled back into the shell and reheated.
You can steam whole potatoes in the TMX, either in the basket or the varoma dish but of course it will not have the crisp outer skin. There is no reason you can't do the first step in the TMX then spray the skin and bake it in the oven until it crisps up. I often microwave large potatoes for a few minutes to cut down on the cooking time in the oven if I am in a hurry. I love jacket potatoes, particularly a crisp skin and can never understand why some people only eat the middle and leave the best part on their plate