Technically, yes, there is room with the 48mmm. My dealer and I discussed and they said absolutely do not use them. Talked to one seller of spacers about how many he sells for BX. He claimed that the majority of his business is Kubota dealers and the majority are for BX. An extra 2" doesn't seem like a lot considering some are selling 3"+ spacers. I wouldn't put any on the front, maybe the rears. Going for max safety here due to my hills and the way I mow.
I think the BX18 has narrower tires than the other BXs so you probably could run 2" spacers.