Well there's still some occasional ghost dots, but I have no idea why
But I've found a way to avoid them.
A couple things:
Make sure you have your chat window (the customizable one) to include the "voice" option. That will make all radar announcements appear as text and with the mission there will be plenty of announcements as there are plenty of bombers flying around
I've found that the radar only pickups moving planes (aka real ones!). The other thing is if you approaching a group head on and they don't appear to move across the sky, then they are more than likely a ghost dot. Lets just say, I've yet to see a ghost dot move. They are usually suspended in the air for w/e reason.
But definitely turn the radar part on in your chat window. And for the sound issue make sure your voices/speech tab under the audio controls is unchecked/muted.