We've also got a lot of (possibly Extended Squitter?) data at
ADSBexchange.com published as "unfiltered" for those who know what it might mean. I've spent a couple of hours looking at it this last evening and there are lots of raw plots seemingly reporting exactly 1000' separation during the descents at the relevant times which I think were around the couple of minutes 1311-1313Z on the day? What I can't quite understand is the exclusive use of ½ flight levels in a large part of every ADS-B data record or collection of "squits". Someone will know what that is.