cfl Wiring Rules/Norms

→ British Standard 7671.

Circuit conductor size is related to the method and sizing of the circuit overload protection device and both the method and length of the cable installation.

All it means is that a larger number of them can be connected to the circuit that used to supply 60W incandescents, as CFLs are smaller individual loads.

Rule says, A circuit of 2x2.5 sqmm(ph & Ntl)+1.5sqmm(earth) can carry maximum of 1000 watts. you can use 1.5 sqmm wire for individual switch control.

Using smaller conductors to provide juice to a CFL is not necessarily a bad idea. You would have to provide a disclaimer to anyone in the building/home that only CFLs or fixtures of X wattage could be used. This may discourage someone from wanting to rent/buy the space.

What happens if CFLs fall out of favor and incandescent lamps cannot be used because they would overload the circuit/cable?

Someone could mistakenly replace a lamp with something exceeding the design limits. Who know, maybe cause a fire?

Seems that using what is common in the trade would be the prudent thing to do.