Well I don't want to promote a site but True Achievements web site could probably do a conversion. Through some agreement, they are the only ones that have access to xbox live cheevos API. They do calculations based on how many people on their site got that achievement and have a true achievement number. They could connect into the VS Cheevos and add that to your total, but an TA number or ration is not the number that you floss on your windows phone at clubs. It would be much easier for MS to just add it to the Xbox live ecosystem.