to be clear, UA only issues 016 tickets, whether or not a UA segment is on there. The potential challenge is getting a UA agent to book the ticket without any UA (operated or marketed) segments. Some have reported trouble with.

IIRC, I think I did actually see an LH PE fare come up on UAs website once - probably a couple of years ago almost. I’m pretty sure there was also a UA segment involved (since I’m not based at an international gateway city, there always is). I think it was when I was making a booking to BLR, and there were some options that showed PE, even though I wasn’t looking for it. Didn’t do anything to make it come up - just kind of saw it.