It's been a long time, but I would have thought that with the CB plugged into the A set, you will get whatever function you ask for from the harness.
ISTR options included Work A / Monitor B, Work B / Monitor A, Work one set or the other or I/C only. With two sets selected, working set in the left ear, monitored set in the right. With I/C selected (was it a separate switch?) it came up in the right ear.
When I transferred out I soon had a hearing test. I was told I was 85% deaf in my right ear. Best part of three years later they came round and ran the tests again just before my next posting and told me my right ear was now fine.
I came to the conclusion that seven years of live I/C in my right ear as we cabbied across the countryside, wind whistling through the live boom mike had done for the ear. Three years of not having it whistle and everything was fine.
Still makes a good excuse for not hearing her indoors though.