For intra-Europe flights, are there any benefits that a US Airways Gold member receives on a BA flight?

I'll be traveling from London to Italy on a hand baggage-only fare. Do I have to pay to check a bag as a gold, or will I be able to get one checked for free? The benefits chart on BA's site says that OW Sapphires get an extra baggage allowance, though I'm not clear how that applies to hand-baggage only fare. I'm not expecting to get two or three bags for free, but it sounds like I'd be able to get one at least.

I put in my US DM number at booking, and it did let me select seats in advance, but it seemed like it wanted to charge me for a bag. Not sure if it has any impact on this situation, but on a recent flight, my AA BP still showed me as a OW Ruby, even though I was gold on US. US's website and boarding passes reflect gold status accurately, but I can't tell on BA's website what it thinks my status is.

Any help or info would be much appreciated! I tried searching around here and Google for a clear answer to this, but I haven't found one. (Searching for "British Airways" turns up a lot of US Airways threads here, since it matches on "Airways", and "BA" is too short...)