I would like to know where it is required to use bx when wiring is fished? The BX cable can do a lot of damage to loomex when it is fished into a cavity where loomex is.
If anything we would actively discourage it and i might even require a contractor to open a wall to prove the bx did not damage loomex already there. A loomex cable sliding across another in the wall is no where near the risk that pulling a bx in would create.
Now if loomex is installed in a T-Bar ceiling we require the drop from the ceiling to the fixture in the t-bar to be wire with bx so that when a guy comes to install a bunch of data wire he won't damage the fixture drop wires. Not much loomex gets installed in tbar ceilings since most t-bar ceilings are used to move air which requires an ft-4 rating and I believe loomex is only ft-1.
12-612 Proximity to knob-and-tube and non-metallic-sheathed cable systems
Where armoured cable is used in a building in which concealed knob-and-tube wiring or concealed non-metallic-sheathed cable wiring is installed, the cable shall not be fished if there is a possibility of damage to the existing wiring.
Armoured cable must not be fished in locations where concealed knob-and-tube wiring or non-metallic-sheathed cables have been installed. The armoured cables may damage the insulation on the conductors or cables, causing arcing or shorting and creating a potential fire hazard or loss of power to circuits or equipment.
