I decided to go ahead and book an alternative for my JNB-MRU segment in Business Class on AA award ticket (YUL-DOH-JNB-MRU) for late October).

As this is now the second major disruption of operations at Comair this year, I didn't want to leave it to chance. I prefer to have peace of mind and not bother with the hassle of keeping on top of the situation and then chasing after BA/Comair or AA.

Being that my ticket was issued by AA (BA will not touch the booking) the only option AA offers is to cancel the booking, refund the taxes and reinstate the miles for free.

I kept the YUL-DOH-JNB w/ Qatar Airways. I had a separate return booked with Aeroplan MRU-LHR-YYZ w/ Air Mauritius and Air Canada.

Luckily Air Mauritius operates JNB-MRU on the day of my arrival into JNB. I called Aeroplan and they were able to add the JNB-MRU segment in Business Class to my existing booking for an additional 10K AP points. I could have booked it separately but it would have cost 25K AP points.

Hope this helps with others looking for alternatives from JNB to MRU.