While I'm not a fashion or catalog shooter, so I don't know the tricks, the way I would go about it would be to use a mannequin, clear or otherwise, against a solid background. It would be quick work using something like Topaz ReMask to knock out the bra, including the part of the mannequin seen through the lace.
This was my original thought, but after nutting it out, it's just not possible. No mannequin, no matter how clear it is will allow such seamless viewing of the rear of the garment. Too much distortion through the glass (or alike) and too many reflections.