With allowances for marketing types' penchant for making things up on the fly...
You are correct, auto-focus typically involves moving the focus ring of the lens itself, while auto-backfocus adjusts the lens/sensor distance by moving the sensor (or less commonly, the lens mount). The former is a function of the lens, the latter a function of the camera.
In almost all cases, an AF lens is controlled by the camera, and in almost all cases with CCTV, that means the lens and camera are an integrated unit, which potentially limits your lens options to those specifically designed for - and sold with - the camera. I've seen a very few lenses that had remote-controllable zoom and focus independent of the camera, but those merely had connections to power the motors and required some sort of driver to interface with RS-485, AF, etc. You could use something like that and just run wires to the lens to send it the power to adjust via switches or something... seems like a lot of screwing around though, and your selection of lenses would be extremely narrow.
Since ABF moves the sensor even without a lens attached, you can typically use any suitable lens on the camera, which gives you the option to use whatever is best for your purpose. For extreme wide angles, Theia makes some really nice (if somewhat spendy) C/CS-mount lenses.
You're also correct, JUST remote backfocus would probably do the trick... however, I haven't seen any cameras that had motor-driven backfocus that didn't have ABF. I've used manual remote focus on some cameras and it's a nightmare to work with - you'll spend more time trying to get it right than you would just putting a ladder up to the camera.
In most cases with CCTV, both AF and ABF are one-shot triggered by something else, be it a change in zoom, switching the IR cut filter, or a manual signal of some kind. I seem to recall a couple cameras that had a continual AF mode, but I'm not sure what the value of that would be in most CCTV installations, as something passing close to the camera (flying creature of some kind, for example) could conceivable trigger the AF to re-adjust, thereby throwing the rest of the scene out of focus for a short period... or even indefinitely if the camera doesn't "think" to re-focus afterward.