Considering I'm not in the business, just knowing a few in it, I can only tell what they told me. What I know is that redubbing is VERY common in Sweden, well, in Europe in general, unless the distributors orders the dub (like dubbed theater realeases), it's entirely owned by the ones who paid for it. You are right that they could re-dub it if they want, but they can't use the existing dub if Tv4 declines to sell it to them.
Maybe licensing in the US is different or something, I don't know...
Slightly off topic but a non-anime example, Disney's Aladdin animated series, a channel licensed the show and dubbed it, then Disney actually had to step in and pay the channel for the dub a few years after before the channel shut down, otherwise they'd have to redub it. So even Disney who has such a tight grip on their products can't even do what they want with their own stuff. Bonkers has never been aired since the 90s because Disney doesn't own the dub and cannot use it...
TV4 wouldn't have to sell it since in short terms, they were producing it for Toei. Toei owns it, but TV4 is the company that actually created it. Individual dubs aren't on separate copyrights. They are all on the same copyright as the show itself. When you license the rights to the original series, you can pretty much use any international dub you want, though they aren't free. Of course, another issue is that the actual film elements for said dubs have to be housed and stored. Now, it's very possible TV4 does have control over the actual film elements to the audio of the Swedish dub. They just wouldn't be able to broadcast it unless they first license the broadcast rights to the series from Toei. If any other distributor internationally would (for some reason) want to use that audio, then Toei attempt would track down the masters (unless they have copies themselves) and let the distributor use it without TV4's permission (though I'm sure they would be notified). FUNimation's DVD of Slayers had a multilanguage feature with audio from as many languages JC Staff could immediately track down the audio for (Spanish, Italian, Mandarin, Cantonese). They didn't use the dubbing companies' permission. Another example is Robotech: The Movie. A&E Home Video was forced to release the film as an extra feature without the Megazone 23 footage since they didn't have the rights to it (or, Harmony Gold USA for that matter. A&E was only the home video distributor), even though the dub for the footage existed.
Disney probably didn't have to PAY for it, but they did probably have to acquire it from the channel if they had a grip on the masters. Disney DID help pay the network to create it (based of what you're saying). As for Bonkers, it's possible Disney can't locate the masters. There might also be clearance issues.
Sorry if you find me annoying, I just find this stuff really interesting. ^^
While I understand and agree that they cannot to anything with their dubs unless they get broadcast rights, I find it hard to believe Toei owns it, I'm sorry, but it just seems strange considering dubbing history over here... I like your example of "Slayers", but it feels like if the distributors didn't order the dubs from each country, they should at least clear the rights for each dub with each owner (not dubbing company).
I'm not sure how the dubbing process goes in the USA, but it seems like they have more power than here for some reason...
As for Bonkers, I actually watched an interview with the main actor and he said this (translated): "Some tv channel has the copyright for it, and Disney doesn't, they haven't bought it from them. In the beginning of the 00s, Disney bought all the dubs of all series and movies made in the 80s and 90s. They send a list of the actors in the dubs and paid us accordingly, because they hadn't done it before. Disney doesn't own our voice work."
He says Bonkers wasn't as important to Disney as Aladdin, so they never cared about buying it, so it's now in copyright hell, since the channel doesn't exist anymore.
Considering we have several dubs for Flintstones, Scooby-Doo, Jetsons, Turtles, Tom & Jerry Kids, Rescue Ranges, DuckTales and many, many more, it can't be as simple as the distributor owning the dubs, especially since all these series dubs was ordered by one channel, and are known for refusing to let their dubs being used by other channels and released on VHS/DVD... Rescue Rangers in particular, TV3 ordered the dub from the dubbing company they always used, dubbed all episodes, and a few years later, Disney stepped in and re-dubbed it all with a different company since they didn't own the other one.
I am intrigued by all this, I will ask my friend who owns the biggest Nordic dubbing website and see what he says.