I'd been watching downloaded episodes of MythBusters for a while before it finally turned up on (free) TV here in Australia. It showed on SBS, but in a strange local version.
It was dubbed.
Well, the whole thing wasn't; it wasn't as weird as Iron Chef (also on SBS!). But the voice-over was redone by someone with an Australian accent, for unclear reasons.
The words were pretty much the same; maybe some metric units instead of Imperial, but the Australian voice-over still talked about "gasoline", not "petrol", for instance.
(Usually, "Australianised" versions of shows are things like nature documentaries "presented" by some local talking head, who just does intros and outros for some cheaply licensed, usually American, show; the in-show voice-over doesn't change. Wholesale revoicing is usually reserved for local versions of TV news pieces, often with the Aussie voice saying the exact same thing, at the exact same times, as the original US/UK/Ukranian journalist/corporate shill.)
The SBS MythBusters was also re-edited, which is actually a good thing. MythBusters was made to have ad breaks in it, and so it's got a sliced-up structure; you get the first bit of the first story, the first bit of the second story, maybe the first bit of the third story if there is one, teasers for what's coming up, the ad break, a first-story recap, the second bit of the first story, a second-story recap, the second bit of the second story, et cetera. This requires some seeking-forward to watch adless downloaded versions with maximum efficiency.
SBS only has ads in between shows, though, so their version deleted all of the recaps and teasers, and had each story is one solid lump, followed by the next. This was a considerable improvement, if you ask me.
Perhaps they needed the new voice-over to cover the re-edit. I didn't perform an exhaustive comparison of the US and Aussie versions of an episode to determine whether this is the case. And now they're showing the regular sliced-up US-narrated version of the show, anyway. I think only the first season was Australianised.
And the saga continues. Now edited excerpts from MythBusters, once again with (the same) Aussie commentary, are turning up as filler in "Beyond Tomorrow". That's the renamed-for-the-second-time sequel to Beyond 2000 (the Beyond Tomorrow URL is still beyond2000.com...), which was known in its original incarnation as Towards 2000, back when 2000 was a reasonable way away.
There's an explanation for this. Both MythBusters and Beyond Or Possibly Towards Whenever are productions of Beyond International (beyond.com.au). Beyond are at least partially responsible for a large number of variably memorable TV shows and movies (their cinematic high point is probably their shared production credit on Strictly Ballroom, though their hand in The Wiggles Movie may eclipse it). Hence, small doses of MythBusters as incongruous gap filler in an Australian sub-Popular-Science TV show.
Beyond's Aussie connection is also probably responsible for the clearly Australian producer who gets a line or three in the recent special episode, "MythBusters Revealed".