Oh gone on then you can make your RT call but just make it factually correct.
"Roger, I have an unidentified contact on my unapproved TCAS unit which may or maybe not be the traffic your on about G-xy"
In the open FIR in a none Radar enviroment you haven't a clue whats out there. And have no way of knowing what you are picking up on your box of tricks. Or more to the point what your not picking up.