I’ve not fetched subtitles in a while but back when I did, I recall all the websites hosting them were extremely protectionist… more so than any other category of content on the web.
Of course the fix is to have torrents for the subtitle collections, perhaps by language.
The others are right. Trying to stream from a torrent seems wasteful and complex.
But if you must for some strange reason, perhaps it would work to use webtor.io to produce an http-reachable audio file which could be curl/wget-fetched and piped to an audio decoder/player. I doubt you could make webtor fetch pieces linearly from the beginning. You would likely have to wait until the last piece is fetched to start streaming.