Not very clear? There is nowhere on travel bank T&Cs that says they can't be used on codeshares. But no, the option usually won't show up when booking.

When I was booking to BKK in August (for a December trip), with an NH segment as one of the TPACs - here's what I did. I held the ticket (using pay with cash - I think) and then kept calling. It took about 5 or 6 calls to web support and reservations, but they eventually ticketed it for me.

The first few calls, I got told they couldn't use it because of the codeshare. I told them that was unacceptable as the terms didn't mention this anywhere, and that certs you can't use on codeshares always specifically mention this.

Finally, got a reservations agent who agreed this was the case. She first spent about 45 minutes trying to manually add it, then took my info and was going to work on it for means call back. Within 2 hours, she called back saying it had been ticketed, and that the travel bank funds were still in the account, but would come out within 2 days (used a credit card to pay for the balance).

I pressed so much on this because we weren't talking about a few bucks, but about $1500 from a gift registry my wife and I set up so we could use it did our honeymoon. Not sure, really, what is so difficult about either putting no codeshares on the T&Cs, or allowing the use. I presume I got lucky with a great agent - and that this is very YMMV.

Interestingly enough, day before we left I booked a domestic trip involving US air segments on the UA site, and wanted to use a TCV to cover a portion. Didn't think I would be able to (said some codeshares were allowed) and surprisingly, had the option for gift cards, travel bank credit, etc. was able to successfully apply on the site, and seemed to go through. Titan email shortly after saying ticketing was taking longer than normal, but would confirm within 24. 24 hours later - another email saying they couldn't be used. Was able to ticket by calling and paying total on CC.