In most cases, releases in the same release group would need the same (locale) aliases as the titles would be identical. If releases inherited aliases from their shared release group, the data wouldn't need to be duplicated manually?

Example:
http://beta.musicbrainz.org/release-group/0daff82e-cd28-44d8-bf6a-ffe1e56ccb31 has 4 releases so far (and it is yet incomplete), and they should all show the alias on http://beta.musicbrainz.org/release-group/0daff82e-cd28-44d8-bf6a-ffe1e56ccb31/aliases