It would certainly be an interesting thing to know. Back of the envelope for ICE is ~20% from tank to wheels, From coal plant to wheels of an electric vehicle you'd be looking at line losses first, then AC/DC conversion losses (5% or so) in the charger, battery loss during charging (Ri of the battery comes in to play both ways), again during discharging and then probably a better figure for the drivetrain of an electric car versus an ICE based car because it is much simpler, but the motor would still lose some energy to heat due to its internal resistance (another 3% or so).

Thermal efficiency for a coal plant is ~35% give or take (depending on how new the plant is) so that would be your starting point.

Charge/discharge losses for a large (20KWh) pack that I used were around 25%, a modern EV might do a bit better but probably not that much better (because the internal resistance of those cells they use is quite high).

Putting all that together:

    .33 * .75 * .95 * .97 = ~22%, and ~24% for a high 
    efficiency coal plant.

With line losses un-accounted for because they vary very much depending on the location of the plant and the consumer.

So it's actually pretty close, better than I expected.