Can turnouts be used as a form of cab control?
Yes, in a way.
The system is known as MZL, and was originated by the late Ed Ravenscroft. It took four articles in MR to describe it about forty years ago. Much of the hardware Mr. Ravenscroft used is no longer available. (When was the last time you saw a Varney slot car controller?).
It requires having contact sets on whatever moves your switch points, and is very wiring-intensive. A knowledge of Boolean algebra is also useful. I have been using a modified form ever since those articles were published, but I can't recommend it for new construction.
You still have to select a cab to each master block. The point contact circuits then extend that selection to the 'city limits' of that particular station.
Chuck (Modeling Central Japan in September, 1964 - analog DC, modified MZL)