In my experience, LTO-4 tapes encrypted with IBM drives can be read on HP drives, but not vice-versa. The IBM drive I have hangs and resets the SCSI bus when attempting to decrypt a HP encrypted tape.
I’ve tried a ridiculous number of combinations of SCSI parameters to the encryption, decryption and read. I’ve also tried all available firmwares for both drives.
However IBM drives will happily read the raw data, so my current weekend project is to try and reverse engineer and decrypt this in software. Update: Finished! https://github.com/lukefor/ltoex – more info here: https://darkimmortal.com/the-secrets-of-lto-tape/
So much for LTO being a compatible and open standard!