It should work, although you may still have some "flickering" of the rear headlight. There are some light systems out there that have a capacitor or something so when the wheels lose power for a second it keeps the light lit...I think there are some battery powered lights that also can be set up to be recharged from track power.
If you run the two engines together (as you normally would in a cow-and-calf arrangement) you could also run two small wires back from the powered engine and use that to light the calf.
If you're in DCC, you could get a powered chassis with headlight and replace the dummy calf chassis with a powered one, install a decoder, then set the CVs so they run together as one unit.
I don't see why it wouldn't work. If you are using DCC, you should add a diode and resistor in series with the LED. I would also be inclined to replace all the plastic wheels with metal ones.
Elmer.
The above is my opinion, from an active and experienced Model Railroader in N scale and HO since 1961.
(Modeling Freelance, Eastern US, HO scale, in 1962, with NCE DCC for locomotive control and a stand alone LocoNet for block detection and signals.) http://waynes-trains.com/ at home, and N scale at the Club.