I haven't needed to do this myself but have a few ideas if you haven't already tried these yet
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Are you trying to mount as HFS, or as iso9660? Those CD media you are looking are are probably hybrid ISO/HFS discs so they technically can be read in either format.. I suspect mounting as iso9660 with/without its mount options could help you copy the data afterwards. Check the man page for mount to review the options, thinking iocharset and/or utf8 could be helpful if the defaults aren't working.
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If the standard mount / cp isn't working you could also give other tools a look. Have not tested this myself but I saw the Debian repo has hfsplus - which includes hpmount and hpcopy which should in theory be able to copy off HFS+ media. No idea if the tool also works with HFS but could be worth a go.