Had BA codeshares all on AA metal last month. 1 domestic, 1 intl segment each way.
Outbound domestic changed departure time twice, and I’ll hand it to BA for notifying pretty quickly of the change each time, and it wasn’t even their metal.
I don’t recall ever receiving such a notification from AA in advance. Always had to find the surprise myself (which is why once a week I take 10 minutes to double check any upcoming flights, regardless of carrier.)
Just remember that if the flight changes by more than 30 minutes, you can call and change to another flight. If it changes by less, but puts you under MCT, you can also change to another flight. Just be sure to have options available to feed the phone agent and you’ll be fine.