As I understand it, releases can share a tracklisting (e.g. http://musicbrainz.org/tracklist/1266911) but if an edit is made on one release, it is automatically given a new tracklisting with those changes.

I think it'd be good to have the option to make changes to the tracklisting so that an issue that applies to all releases can be easily rectified without having to edit numerous releases. This could be in the form of a simple checkbox (defaulting to off) in the release editor which allows the changes to be made to the tracklist shared by the listed releases e.g.

"This tracklist is shared by multiple releases. Should this change apply to all releases?" Yes/No.

I think this would alleviate the underlying issue in e.g. http://musicbrainz.org/edit/17774115 where it is being proposed that there be one release (losing release date data), presumably so as to make it easier to make edits to the tracklist of a release which could be shared by many countries.