Starting at http://musicbrainz.org/cdtoc/attach?id=uK3xHMl_h.kIM7bl3STeLrVNN.c-&tracks=9&toc=1+9+171151+150+21600+39450+60525+77550+98100+118050+136950+150750&tport=8000 I wanted to add the second CD to http://musicbrainz.org/release/d9b19aef-6075-424c-a1ce-7548d10b3bba but that appears to be impossible, the only options are adding the DiscID to the existing track list (because the number of tracks match) or to add a completely new release.

Workaround appears to be manually adding the second disc without track times, adding DiscID, setting tracklist durations from DiscID, then making a bogus edit (MBS-4820) to propagate the times to the recordings.

Without snark, I note that new users would probably either add a second release or just give up.