Yes, for upgrading AA marketed and operated flights with AA miles, EF can search for that space.
Book AA marketed and operated in economy, then use miles+copay upgrades.
Thank you! Do you have any advice regarding how to best search for flights you can upgrade with miles + copay on EF? Just keep searching different dates within the Awards and Upgrades availability section until you find a flight that shows available seats for upgrade on the far right column of the results page? I'm selecting to search for
Business - Upgrade (Including 2-Cabin Domestic First) (C).