It is remotely possible that there's an
undocumented "format" command in
the protocol. However, I've heard multiple people claim that special
firmware was required.
As far as I can tell, the TU58 drive hardware should be perfectly capable
of formatting a tape, unlike e.g. disk drives that use embedded servo.
If someone wills to create a formatter, I'd like to keep informed. I
always had curiosity of how these things works :)