The questions only concerns the following languages:
English, Dutch, French, German, Italian, Japanese, Korean, Portuguese, Russian, Spanish
After reading YouTube's official documentation, it would appear that all videos have automatically generated subtitles. However, for example this video doesn't have captions of any kind.
Review, edit, or unpublish automatic captions
If automatic captions are available, they'll automatically be published on the video. Automatic captions may not be ready at the time that you upload a video. Processing time depends on the complexity of the video's audio.