Yes has to be an EI e-ticket. Which is fine, except you can't say book PE on BA/AA when booking through EI so you're basically committing to either Y or J. With the new TC changes & mutual recognition of status between EI & BA/AA, would love to see this harmonized as well, i.e. voucher upgrades & companion tickets valid on BA/AA issued ETKT, with a TATL segment operated by EI.