Well, it clearly depends on what circles one moves in, what one reads and what TV etc. one watches. Maybe you don't watch Newsnight or business-related programmes!
I see and hear it used quite a lot, but only ever with the meaning that stillp assumed (Small or Medium Enterprise). If you type "SME" into Google, nearly all of the first few pages of hits (and maybe most of the rest of the 100,000+ hits!) relate to that meaning. I gave up trying to determine what page one had to get to to find a hit which assumed BAS's meaning!
Kind Regards, John
It is on the first page returned by Google in the right hand column in the 'See results about' box, second entry. It is a common term in IT and was around in the mid 90's when I had a brief career as a systems analyst, before moving into the electrical installation.