I have the big DVD box set of all their 'adventure' specials and most of the music has changed (if the broadcast version wasn't library music to begin with). I had some fun a handful of years ago looking for a bunch of it and ended up around 150 or so tracks from all over the place.
It starts out reasonably straightforward - the Polar Special almost exclusively uses the Director's Cut library, then for the Botswana special they branched out a bit to other labels at Extreme Music, but go forward a bit more and their editors are using music from every conceivable library, as well as a lot of film score re-recordings by the Prague Philharmonic Orchestra.
One of the most interesting cases for me was the farm section at the end of the Australian road trip, where the library replacements were more interesting to me than the soundtracks.
My music fandom has a crossover with library music and general instrumental soundtrack music, so I'm pre-disposed to often enjoy the music in a show like this.
