I have similar contacts at Vandenberg, and through my former agency's liaison with VAFB. I was aware that the Slick-6 facility was again modified/enhanced to accommodate other launch vehicles, but my understanding was that it had not lost its shuttle capability (not that there are any plans to use it in that way). I had read that they had provided a technical fix regarding the concrete ducts, the fear being there could have been a hydrogen buildup in them. It had something to do with a pre-launch spray of hot water in the ducts.
Here is a good recent article:
http://spaceflightnow.com/news/n0401/18delta4slc6/