The problem is, I'm not sure how many videos being shared out there even have subtitles. And even those that do, might not have a description showing that they do. My guess is there's probably not many videos being shared that have spanish language with italian sub-titles. Ideally, a video search with advanced options selected allowing Language: xxxxx, Subtitles: xxxx & perhaps title either - .mpg or - .avi
But as suggested, there's probably not even so many english videos out there being shared that give a description that they have subtitles of another language. A very small % I'd suggest. And overall, very minimal. Bitzi may sometimes show whether a video has subtitles or not & in what languages.