The sensor behind the emblem is used for distance for Distronic, but like you said the stereo cameras at the top of the windshield are used for lane centering.

 

That's what I thought as well. But recently my Active Steering Assist (aka Lane Centering?)

went completely inactive and I found a grasshopper stuck to the camera (below the emblem on the grill). I removed it, cleaned with alcohol swabs, and my Steering Assist returned, although poorly.
(I don't use Lane Keeping Assist because of the brake-centric implementation.)

(You can see the barrage of chips in that lens!)
I could still see a smudge on that camera, and looking further I saw the chips. The shop couldn't calibrate that camera, and they were able to warranty it. I don't have the car back yet.
The technician said that he observed my complaint on an extended test drive before the replacement, and it was gone after replacement and recalibration.

So that made me question my assumption that the stereo cameras in the windshield direct the Steering Assist.

FWIW, another thing I also don't think is related to steering assist is my rain sensor. I complained about its irregular function and they found "GEL FOR RAIN LIGHT SENSOR IS NOT SUFFICIENT."
So it was replaced
and recalibrated as well. The gel referred to was an adhesive gel, and apparently the rain sensor had sagged. I'm on my fifth windshield so perhaps an installation wasn't correct.

Anyway, this thread was about Automatic Lane Change. My car is too old for that.

But since the car convenes every night at 11:00 p.m. to plan the next day, you never know.

 

That is interesting, but at the same time doesn't add up. On certain models the Driver Assistance Package and the Parking Assistance Package are separate and you can option one or the other or both. The Parking Assistance Package is what adds that front camera, so it won't be there if one options just the Driver Assistance Package, yet LKA etc. are still functional. Perhaps the software takes advantage of everything it can. If the camera is there it factors it in, but if it's not there it only relies on the windshield camera. Who knows. I would expect they protected it better if it is actually needed for LKA to fully function. My hunch is what actually fixed it is replacing the gel pack. For that they had to take apart that entire overhead unit where the stereo camera is and recalibrate afterwards.

 

That's a great idea. I wonder how much they charge for a 3/4-in PPF. I'll definitely check.
Mine was certainly sandblasted.