Closed Captions are not separate streams, nor are they burned into the picture, they are interlaced in scanlines IN the picture - this a strange American idea, not really used elsewhere. Though you can buy DVD's which has this kind of subtitling, usually people outside the US can't see the subtitles, and may not even know there are some in the file.
CCExtractor can extract this information from VOB's by looking at the TS metadata: http://ccextractor.sourceforge.net/
