I don't know if this has been reported already, but I was just able to pull up my UA code-share flights on ANA for the first time.
Signed into my ANA account. First name with middle initial attached. They give me a new reservation number (different than the one UA gave me).
I can see my seat assignments (which I already called into ANA), but cannot change them.
When I try to register my passport info, I get an error message for 3 of my reservations, but it works for another one (which is booked in Z).
I am able to email myself the reservation.

Not perfect -- but better!