I understand completely the issues relating to verification of Mode C, and it is pleasing to see that the general line in this thread is in agreement. It is worrying that pilots are seemingly relying on ACAS as some sort of AI radar.
Back to the Mde C verification issue, it is absolutely the norm for mil ac operating with ASACS units to be verified within the first minute or 2 of arriving on frequency, and this process seems to be well understood by those we work. Just a couple of Qs, though, when an ac takes off from a large airport, who is responsible for Verifying its Mode C? Presumably the first agency capable of reading it whilst in 2-way comms, but these are busy places at a busy stage of flight - does it always get done?
I promise I am not digging here, it's just out of interest.
STH