Boora
Think you'll need to consult AS3000:2007 assuming that is the current issue in Oz.
Here in the UK BS7671 still permits the use of screwed steel conduit, trunking, SWA & MI sheath to be used as a circuit protective conductor (ground wire) in final circuits subject to compliance with EFLI values. A fly-lead tail from mounting boxes to wiring accessories and light fittings is required as you describe.
However although our regs permit this use most specifications call for the installation of a separate green & yellow conductor for each circuit.
It would be pretty much unheard of to rewire an old steel conduit installation and not run an earth along with the circuit conductors. Most sparks would not trust the integrity of old steel conduit - which is typically black enamelled & prone to corrosion - especially where it is concealed within the building fabric.
