You can upgrade on ANA metal if on a Y or B fare (no code-share) and you are willing to spend the miles. I believe in this context Air Japan is a wet lease d/b/a ANA and it would also be eligible, but I'm not 100% certain.
http://www.united.com/web/en-US/cont...rade/saua.aspx
Also of note is that currently *A upgrades aren't available so you might have to wait a bit more until they get that functionality back online.