Can electroluminescent (EL) wire used as a conductor?
The wire has some resistive leakage between the two conductors. Even if you were to 'float' the EL drive with a transformer and use the wire to carry another signal, enough noise would couple to the signal to spoil it unless it's very low impedance.
Even if there were no resistive leakage, the current flowing back and forth charging and discharging the wire will have some AC drop across its length. For a long piece of wire that might be a lot, and this will show up on your signal.
So, yes, it might work for an LED. But for any signal you really care about? Too much coupling.