Hi,
About one month ago I called the Elite line (Silver Elite) and talked to a nice lady. I wanted to buy a ticket IAH-CDG and upgrade to BF with miles. I told her that before buying the ticket I wanted to be sure that the upgrade was available. She checked and confirmed to me that such an upgrade was available and so I went ahead and got the ticket and she did the upgrade at the same time. No problem there. So I think you may want to call and check on that.
I hope this helps,
dc.