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That's a very good question. "True" translations which require editorial input (that is, for example, a translation from French to English, where every word doesn't have a 100% identical counterpart and discretion is needed to choose the appropriate word / phrasing for any given sentence) are copyrightable. So even if a work is outside of copyright (think old greek myths, which are in themselves public domain) the translation could still be copyrighted.
Braille, on the other hand, is a reproduction / conversion of the book into a different format. It's the same letters, wording, phrasing, etc... rather than using editorial discretion in choosing which different words are used to convey a meaning that doesn't necessarily translate. So a Braille conversion / reproduction of a work is not copyrightable in and of itself. Now if the work was in a different language and you translated it in your mind prior to reducing it to Braille, that would be copyrightable (as it would be a true translation). But without translation from another language, it would just be a conversion / reproduction, and would not be copyrightable as a new work.
Hope that clears things up a bit. If you have any other questions, please let me know. If not, and you have not yet, please rate my answer AND press the "submit" button, if applicable. Please note that I don't get any credit for the time and effort that I spent on this answer unless and until you rate it positively (3 or more stars). Thank you, ***** ***** luck to you!