Well - I know that the Blu-rays I've tried do have subtitles.
I've just put a Blu-ray into a BD drive and used MC17 to play it from there. Same thing, subtitles are "n/a". The disc is the Dutch version of Avatar, which has three soundtrack versions (English, French, and German) and four subtitle languages (Dutch, English, French, and German).
Something isn't working, I feel...