FWIW British channels do it when it's cheap enough - The Deadliest Catch has a different narrator for the US and UK broadcasts.
This irritates me to no end. I'm sure it's just because I'm used to them, but I love Mike Rowe's narrating for the Deadliest Catch, and I love the guy who does the US version of Mythbusters.
Then I go visit my folks in Holland and we end up watching a lot of Discovery because my wife ofcourse can't understand the dutch television. And the narrators are different and it just grates on me. Especially since the UK narrators are, imo, nowhere near as good as the US ones.