We were having a discussion about this problem as our routes are close to military practice zones. We fly RIS /RAS and with that are provided with some cover, but comparing notes we all have AT LEAST 2-3 "avoiding action" EACH with military a month. My concern was such to raise it as a topic with ATC forum. Very helpful they were too. Yes frighteningly sometimes at 5 nm "passing down your left side" we see....NOTHING. Sometimes we see them in advance of ATC positioning (once passing below and ahead of us, when ATC said they were behind going away)....... of course because of the lag in ATC radar didn't pick up his 180 turn. The wx radar does help in a way as you can see the interrogation traces come up. But does that paint the full picture. I don't know.
I applaud any improvements that could be made. Military have to practice, and one would like to think that they aren't all doing TC's Top Gun antics. Certainly in LATCC military are integrated with civilian controllers, but anyone caring to watch the North Sea area (Clacton) as I had the chance to, will realise the complexity of having to deal with everything from fat alberts, to dogfights overspilling out of DAs, low level around the Kent coast, all interspersed with civilian traffic.
Guess we'll still keep good lookout but frankly relative velocities at 900kts+???? What chances.