This is a good one. If the MI cable is single conductor in a harzardous location then 18-062(2)(a) applies. If it is multi-conductor MI cable, in a hazardous location, then 18-062(2)(a) does not apply and 12-706(2) does. This is to prevent sheath currents from being a problem in a hazardous area. If it is a non-hazardous area then 12-706(2) applies wether the cable is a single or multi conductor.