User blog comment:B214/Question and Answers 3/@comment-82.114.89.218-20140722204824/@comment-5917000-20140723085510

Try looking at it this way ,

The sacred gear itself become detached from its user,just abnormal,even if its user were to get BB he would get the same BB(thats y i said its original).

The abilities of regulus did not change nor it took abilities from any other Sg its abilities are its own,and saira cant probably use the sg's abilities other than outer defence as we saw in saira vs issei.

Now to put it all together, saira is just putting the BB garment thats y its not Sub species.