While perusing the U.S. Copyright Office's website, I found that they'd recently added a ton of listings for the first 65 episodes of the original/DiC dub (records for the remaining episodes, movies, the Viz dub, Crystal, most of the manga, etc, don't appear to have been digitized yet) so I decided to look through them. For the purposes of this thread, I'll be using the first episode ("A Moon Star is Born") as an example.
The episode's copyright was first registered on May 7, 1996, with "DIC Productions, LP, employer for hire" given as the work's author and copyright claimant.
A few years later, a copyright security agreement was filed on November 29, 2000, listing Chase Manhattan Bank as a second party. This was presumably done in preparation of Andy Heyward's buying back Disney's majority stake in DIC.
This agreement was then terminated on August 15, 2008 and a new one was filed on September 17, 2008, listing the Royal Bank of Canada (Toronto) as the second party. Again, this was presumably done pursuant to DIC's merger with Cookie Jar.
The most recent records were registered on May 30, 2012 (listing Cookie Jar Entertainment, Inc., and the Royal Bank of Canada as the parties involved, and on September 25, 2012 (listing only Cookie Jar and its subsidiaries). Again, this was presumably done pursuant to Cookie Jar's merger with DHX Media (now WildBrain).
This would all seem to suggest that DHX currently owns the copyright to the original DiC dub. (The status of the copyright on the movies and CWi dub, I'm not sure about.) Presumably Viz would need to work out a deal with them first if they wanted to re-release at least those episodes, but also presumably, DHX/WildBrain could simply try to work out a deal with Toei to release the old dub themselves. Maybe it's time to start a campaign?