JNB-ADD (738) - 380 USD no bid
ADD-EWR (788) - 800 USD accepted
YYZ-ADD (359) - 840 USD no bid
ADD-JNB (788) - 380 USD no bid
it was possible to bid until 24 hours before departure. I got the email about 22 hours before. The ticket was reissued into booking class Z, which would earn no miles, however I got the original booking class O credit posted to my TK account.
Warning 1: the check in staff at JNB was unable to issue the boarding pass for my upgraded 2nd segment, they only put me on standby. It was only in ADD that I got the seats assigned by the lounge agent.
Warning 2: regardless if you upgrade or not, watch out for aircraft swaps. The aircraft type on JNB-ADD changed 4 times since the time I checked in online and boarded.