Yes, they are; that's the difference between Sugino MW-68 and MW-70 spindles. As I said, Sutherland believes that they're a similar taper to Campagnolo, pre-1992. But just using a Campy spindle in the 115 mm length may not work just right, because the distance between the two bearing tracks, and the location of the bearing tracks on the width of the spindle (symmetrical? non-symmetrical and by how much?) is probably somewhat different. If you want theoretical answers to stuff like this, you need to get and immerse yourself in Sutherland's, which is quite complete on the subject. If you want real-life answers, of course, you need to get some spindles, cups and BB shims, and immerse yourself in trial-and-error. There's no simple answer where BBs are concerned.