Well, speaking generally it is, but subtitles that come with, say, physical version (e.g., DVD) of a TV show or movie, or those that appear in theater, are separate from the "Closed Caption" option that you enable on your TV.
Well, I've never done a test, but I bet if you get a DVD and choose the "Subtitles" option in the DVD setup, and then turn on Closed Captions on your TV, you will get two separate sets of stuff appearing.