According to http://wiki.musicbrainz.org/XML_Web_Service/Version_2#Browse

"As a special case, release also allows track_artist, which is intended to allow you to browse various artist appearances for an artist. It will return any release where the artist appears in the artist_credit for a track, but NOT in the artist_credit for the entire release"

(Minor issue, shouldn't it be track-artist with a hyphen for consistency with release-group and everything else in the WS? And howcome track_artist isn't listed in the "box" above against "release" - should it be?)

If it's supposed to work, howcome http://www.musicbrainz.org/ws/2/release?track_artist=00ed154e-8679-42f0-8f42-e59bd7e185af gives an error? It seems like it should be valid to me.

http://musicbrainz.org/artist/00ed154e-8679-42f0-8f42-e59bd7e185af/releases?va=1 indicates there are several hundred VA releases for this artist.