I'm afraid we don't. There just aren't any United States standards for this. Technically, foreign language transcription falls within the scope of Formats and Textbooks. The languages that are covered are mostly European languages and those all use the latin alphabet, usually with some accented letters. Knowledge of the language is not necessary in order to transcribe it because the alphabet is the same. Russian, Hebrew and Greek also have United States standards and those languages DO require that the transcriber know the language because the alphabet is so different But there are established United States rules for those languages that include dot assignments for each letter and formatting. To do Chinese, the transcriber would have to be knowledgeable of Chinese braille standards as done in China, and I guess that would also mean knowing the dialect as well. A transcriber doing foreign language in the United States is certified by BANA (Braille Authority of NORTH AMERICA) which unfortunately does not include China.
I have not researched it, but it is even possible that braille in China requires that the material be modified to the latin alphabet before it can be done in braille. I think I read that some place, but I'm not positive.