Not sure what all the concern is about. These aircraft will still have to be equipped with transponders so will be 'visible' to TCAS equipped traffic. Do we know if these VLJs are able to respond to TCAS warnings within the expected parameters of Rate of Climb/RAte of Descent?
I would be more concerned by the implied suggestion that European ATC is so poor that TCAS is now seen as an integral part of safety and not just the final safety net it was designed to be.