I'm not quite sure about this, but, well,
I think most of the time, when a movie or tv series is subbed by the country of origin, it is usually correct and other versions will copy the subtitles. (I think this is rare in Japanese TV shows) Subtitles from Hong Kong vary in coherence, some are correct and acceptable, others are downright wretched, and others are correct, but the subtitling itself is wrong. Taiwanese versions, sometimes do not have english subs, and if they do, usually it is from HK. Korean subs are usually good (With a notable exception of Battle Royale : SV), but extras, more often than not, have no subtitles. Althought, don't take it from me, I'm sure many people out there have more experience in buying asian releases.