i would carefully look at BMW wheels before trying to get them to fit your XT. they are great wheels, but look at the angle of the spokes between the rim and your hub, and make sure they will fit. i have put 17" MORAD rims on my original hubs and even that slight change in angle can cause the spokes not to line up properly.
with the spokes on the outer edge of the rim, the angle will be a lot different.(BUT, it maybe a change for the better? i dont know, someone please spend a fortune on BMW rims and answer this question!!)