Yes, you are right, my bad, I did not respect, that we are talking about DOS command files.
A command file should not, must not be coded as UTF-8, even if prepended with the correct BOM, it simply does not work.
So you have the problem how to export language specific special Unicode characters from the Mp3tag Uncode application down to DOS codepage related environment and up to some other Unicode related application.
Anyway this could be done, possibly with the loss of accuracy on special characters.
How this could be done is demonstrated in this cmd script in this thread:
batch file to check for missing covers
But there might be other ways to go. Maybe convert Unicode characters before exporting by function $ansi() or write an action group which converts some Unicode characters into a surrogate format U+0000 and re-convert them later back into Unicode characters.
The best solution would be, that the Mp3tag developer Florian implements a tag field related export action to ANSI/Unicode text file.
DD.20110128.2255.CET