It all seems a bit hit or miss
Unfortunately it is.
That is why there is such a storm over it because the authorities are increasingly concerned that emotionally it is difficult to justify aircraft without collision avoidance. God forbid a CAT and light aircraft collide - the press would have a field day. Everyone believes all aircraft are under radar control ALL the time and have TAS.
Those in the know beat the authorites with the "big sky" stick to which the authorities havent got a convincing answer.
FLARM has its advanatges but is just too late on the scene. It will never be widely adopted.
I have changed my view, and now think all flying machines should be fitted with a transponder. Prices have fallen, I dont think weight is any longer an issue, (see my earlier link) and battery portable units are around the corner. However, I accept cost is an issue, although I think you will get a mode S fitted in a homebuilt for less than £2K.
Although PCAS will never be certified, not only does it work but the technology could be developed further, and the cost would fall significantly if there was greater uptake. I could imagine the vast majoirty of light aircraft having a directional PCAS unit for less than £500. This would provide as good as it gets solution for GA and gliders short of a fully certified Skyforce system.