1) 110-3(b) does not tell you that you must follow the manufacture's instructions. It tells you that you must follow any instructions that are part of the listing and labeling.
2) There are listed "relocatable" low voltage fixtures and would not think that that cable would have to be buried in that the fixtures are intended to be moved around.
3) If the installation is to be "permanent" then I would require the 6" as shown in Table 300-5.
4) If the low voltage lighting system is not a listed system, then the cable requires 24" of cover.
Don(resqcapt19)
