I thought for sure that either LEED or some state where or the energy aficionados were rampant would have mandated these boxes. Hopefully I haven't given them any ideas.
My state's building code addresses perforations for electrical outlet boxes on exterior walls, which basically requires the use of the foam sealing gaskets behind the wall plates for switches and receptacles on outside walls, but that is it as far as I know.
This doesn't seem to be enforced locally in all areas though. I always use the wall plate gaskets regardless, as they are not very expensive and it seems like a good idea to at least try and stop some air transfer, given the known leakage values through these areas.
I'm still kind of curious though as to how much, if any, improvement there would be if both the vapor barrier boxes and the foam wall plate gaskets were used together.