The instructions and the code are pretty clear unless you have a local restriction.
For a while Amp was even marketing these for retrofits in regular 1&2 family dwellings but that was stopped in 99 or so.
They were seen as a way to fix that old "burned up TW wire in the ceiling luminaire" problem. They said you could splice on a piece of NM-b and shove it up in the ceiling then install an old work ceiling box. They used 334.40(B) to justify it.
(B) Devices of Insulating Material. Switch, outlet, and tap devices of insulating material shall be permitted to be used without boxes in exposed cable wiring and for rewiring in existing buildings where the cable is concealed and fished. Openings in such devices shall form a close fit around the outer covering of the cable, and the device shall fully enclose the part of the cable from which any part of the covering has been removed. Where connections to conductors are by binding-screw terminals, there shall be available as many terminals as conductors.
Someone looked into it and decided these particular devices were only approved in manufactured homes, leaving open the question, what does 334.40(B) really apply to?
