I was a CNC machinist, manager, etc. I went back to school for computer science because I believe CNC machining is about to take a big leap and the industry is going to dramatically shift.
I think there are absolutely some applications of CV. Keep in mind a lot of feedback loops in the CNC process aren't there yet, but you decide how a part is oriented in a CNC machine when you write the program to make the part. The machine can skew the axis, but this doesn't happen very often. Usually someone aligns everything to the machines physical axiis. However, the machines often have a probe that could be used to find the orientation of the part, but you have to program that, too.
So, why not use CV to find the rough orientation of the part, generate an orientation routine, then probe it.
Very often the purpose of the person at the machine is to watch ( where is the part? Is the tool broken? Do the chips look right? ) and listen ( does it sound good, or is it making a horrible sound) as a process control. The parameters of milling could probably be controlled automatically with answering the bad sound and good chip shape questions.