Bxpanded has it right. Also I heard it wont work with 2 digit BX's because there is no place to add the valve that the lever is attached to due to fact the subframe for BH takes up that available area under fender. I thought about adding the rear remote there, but i'd hate to get the valve dirty.
I am not sure if its because the BH taking up the available space but instead using up the hyd. ports for the BH.