Yeah I noticed it fit the BB.
I don't think they are plated, just plain holes. You can dissect other parts in the bins with plain holes, which is how I found out, and it might tell you more.
Yeah it would have to be 2 parts, which is not hard because you just delete some holes in the svg.
Always Gerber view it before production or print it out, because it stops mistakes. It saved me a mistake when I realised I didn't have actual mounting holes, even thought there was circles in the picture. I use free Gerbv.