ST2's have 3 spoke brembo wheels, not marchesinis. the only ST that has Marchis as standard is the ST4S.
They can be persuaded to fit, I think, but you will definitely need different bearing sizes because the ST has a bigger diameter axle, so you'll need bearings with the same outer race diameter as the wheel needs, but smaller diameter inner races to fit the smaller axle on the 888. Either that or you can get your chain adjusters and swingarm modified to take a bigger axle.
I thought about doing the same to my 888, but then realised that the you are never going to get mag marchis on an ST - it's a sport tourer, designed to take a pillion and luggage, so the marchesini wheels are going to be ally ones and probably not much lighter than the three spokers. OK if you just want the looks, but won't offer you any major benefits of lighter wheels
[Edited on 15-3-2006 by Jools]