I know I am just a humble controller so could be absolutely wrong on this, but my understanding was that an aircraft will get a Traffic Advisory on Nil Mode Charlie aircraft but not a Resolution Advisory, so the pilot should query the NMC squawk with ATC. That seems to be the way it works here in the UAE but then again we have very few NMC lighties buzzing around as most of our stuff here is the big stuff, except for a few helicopters buzzing around the oil rigs and islands in the gulf.