Apologies to all, I made a mistake in the previous post.
The DMOD distances are lateral distances, not vertical. There are some vertical thresholds (around 800' depending on aircraft altitude again), but I am unsure if they are triggered with no rates of climb/descent. I will do some more research.
TCAS requires an ICAO approved transponder operating mode 3A. It also requires mode C for RAs, otherwise you will only get TAs. Perhaps that is why the warbirds don't give warnings?