In my undergrad experience and personal experience with people who have been implanted, Audiologist and SLPs do very different things concerning CI's.
An Audiologist is part of a team of people who come together to aid a person in obtaining a CI. The audiologist is in the surgical room usually when their client is being implanted and they will also map the CI a month after implantation. CI's do not just take one mapping in their lifetime, it is a constant thing. Just like hearing aids might need to be adjusted, a CI takes some tinkering every now and then.
SLPs are there in order to help the client understand what they're hearing and facilitate speech.
An SLP is more likely to see a small handfull of implanted clients on a more frequent timeline whereas an AuD will probably see more CI clients but not as frequently.
Hope this helps.