I suspect your source is exaggerating.

The AC/AA deal over AA's equity stake specifically provided for the extension of the AA/CP relationship (esp. with respect to codeshares).

While lounge access and upgrades could come off the table, codeshares are unlikely. Since AA wants ongoing access to the AC/CP network, it is more cost-effective for them to do it on a reciprocal basis, to diminish the up front cash cost of doing so.

As for earning on code shares, I think the rule has always been that you earn miles for codeshares, no matter who they are operated by.