There's some pretty solid evidence then. "He recounts a jump seat trip he made to Oslo during the last month of BA Trident operations (December 1985), where the boost engine was used not just on the return leg (where it was essential in the Norwegian winter) but also on takeoff at LHR to confirm its serviceability" could be taken as confirming the irregular use of the engine. I just wonder if the flight would have been pulled had the RB162 decided not to co-operate.
The aircraft sold to Zaire were 'ZC, 'ZD, 'ZF and 'ZG with 'ZV as a spares back up. None were regular shuttle performers through the 1980s so presumably their RB162s were not decommissioned and they were allocated to European routes.