To be able to fax a text file containing Unicode (especially non-English characters), a suggestion can be found in this mailing-list post. I could not use it, though, because my Unicode text had ASCII-art-tables, and the printing process forced using variable font. I was unable to convert the text to an encoding (using iconv or uniconv) fit for a fixed-size font I’ve had available.
I’ve managed to print the text to PDF finally, which then I was able to fax as I pleased. Unfortunately, I am unable to state the tools used for this task. Sorry.