I do a lot of work in old dwellings in the inner city of Minneapolis, St. Paul. The destinction of what is old work vs. new work is fairly well described here.
On a room by room basis, if 50% of the wall surface is removed exposing the framing then the room is considered as new construction and is wired to the most current NEC in effect. (since the NEC is adopted on the state level, here, that is the 2002 statewide. . .it may be different in your location)
Applying a new covering over the existing covering is not exposing the framing. . .no economy of effort is introduced. . .especially if the new wall surface is intact (taped and sanded) before I'm allowed to start my wiring.
Arguably, if the electrician can get in before the drywall (panelling, wood, whatever) goes on, then the electrician can hack or beat large holes and not have to finesse as much, but a large part of the run is still fished. It is bad planning on the part of the Home Owner if I can't wire until after the walls are finished. . .the HO has to spend a lot more on my labor to fish the wires in.
If the inspector is arguing that s/he should see the support, as if it were not fished, on the new wire installed because of the new drywall present, then all the wiring should be to new construction standard. . .that is, outlets within 6' of the start of a wall and every 12' after, etc.
Now, since this is plaster (on lathe?), if the plaster is skinned off the lathe before the rock goes on. . .its a little harder to argue. Then it is a matter of showing the inspector proof that the Home Owner was done with the rock before the electrical was started. Who's to say that the plaster was off at the 50% or higher level at any one time. The HO could have done one wall at a time over a long span of time.
The lynch pin is that the wiring did not start until the rock was finished.
