Yes, they are written/read in EBCDIC. Using tapeutil you can read 3 x 80
byte records (I think, long time since I had to do it), there is an appendix
in one of the IBM tape Redbooks that describes the format.

It's probably a hangover from MVS tape labelling (which is why the format
is not in a manual AIX'ers would normally read). Once you have the
3 records, you can use dd to display the info - if it's important enough
I can find the spec if you want

Dominic