I heard Sting give an explanation for this, I believe it was in one of the
webchats around BND:
Apparently, the Japanese record industry is having a hard time making money
because of the extent of illegal import from Europe and other markets.
So, in order to make the Japanese versions more attractive to customers,
they often add one or two bonus tracks which are not on the illegally imported
albums.
I guess it makes some sense, although I can't see quite how an imported
album could be more attractive (cheaper, I mean) than a 'domestic' album. Most
other places it's the other way round. I don't think he was referring to illegal
pressings...