Well, I can name a place that starts with a Y and that letter is pronounced like the isolated letter Y.
In south Louisiana you can find the small community called Ycloskey, which is pronounced why-closs'-key. I have to admit, though, that it probably got that way because of linguistic cross-contamination. For a long time Louisiana was a polyglot region with French, Spanish, British, Italian, German, and Choctaw spoken at various times in the same small geographic region. So I have no insight as to where or when that particular pronunciation originated.