sure you can...
also, the BA web site for listing:
https://idtravel.ba.com is very helpful with that.
when you put your ticket number, and list on a flight, if the flight is embargoed or not an affiliate to fly on zeds, the web site will let you know, telling that reason.

By the way, 100% sure you can use the Comair service at South Africa with a BA zed...

It is like flying on american eagle with a American Airlines Zed coupon.