Phone lines do have 4 wires so I suppose technically snd,gnd mic,gnd. but that would take some massive rewiting of the old style phones because they don't work like that, they use 2 of the 4 lines 48V,return. So completely incompatible with the headphone jack on a cellphone.. Plus most POTS phones use the 48V to run their cuircitry, and the cellphone isn't going to be providing what the POTS phone needs to run.

Cute Picture tho...