DMX swallowed up AEI, period. Formats, equipment, everything. All the AEI formats (including the instrumental programming) were maintained by DMX for about a year or so post-buyout, then were killed off. The little bit of AEI that DMX didn't acquire eventually went on to become Play Network.
(It was actually mentioned here:
http://boards.radio-info.com/smf/index.php?PHPSESSID=555e6fcaa012a6dab32787e1d8686846&topic=107740.0 )
I would imagine that, for the most part the "AEI collection" these days primarily exists in the hands of those who held on to the old CD-I discs (of which I, myself, have many) or who tape-recorded the audio off the C-band feeds.