Lot of fixed gear riders use them singly for their front brakes and they can be used as primary levers on virtually any bike using standard road cables. Shims are usually supplied with these levers so I suppose they'll mount securely on mtb bars as well. But since these levers are generally tiny (short) with a high pull rate (for V-brake compatability), they may not give you much needed leverage when used on a loaded touring bike. I would NOT use them as primary levers on a tourer....I would stick with standard mtb levers...
Some standard mtb levers made by Paul for instance have a simple minimalist look but rather expensive...