Yup, been trying to get a B3 over. Gave up.
During my quest, I did come across a importer in So Cal that listed B3 as one of the cars they can import. Can remember the name of that importer though.
Then again there are other things to consider. Remember, bringing a B5 over is just a pixel of the bigger picture.
1. Who is going to work on it? It's a supercharged 4.4L and I doubt dealerships here will want to touch it, unless they are properly trained by Alpina or you are a trained tech who likes the challenges.
2. Alpina parts have to be ordered through Alpina directly or KSK Distributing (which mark up the price).
3. Color-matching. If you get into a fender-bender and you have one of those Alpina colors, it might be a headache to match the paint at a the bodyshop. Maybe, just maybe, one finds a REALLY good shop to do it. Still, it's not the same.
But down the road, I may reinitiate my quest again. I am totally obssessed with the B3 model. And I know I will own it one day.