you can book jnbcpt on united.ca on 016 stock but youre going to pay way much more than if you just book a lcc 1-2 days before departure, which is what i do and recommend. i dunno if you can ink the 016 with 014. but just be aware jnb is a circus with biometrics so book a 4+hr cnx.
This doesn't do the OP any good. He wants to book the JNB-CPT as an AC codeshare to earn AQD. Even if you can ticket AC codeshares on another carrier's stock, you won't earn any AQD, because the codeshare
has to be ticketed on AC stock to get any AQD.