Sorry for jumping in so late to this enlightening and light hearted/serious debate… But.. Back in the “day” (1987) I did some work for a reliable west coast organization. I can tell you that at least back then,(as far as I was aware, and I was the paid mashgiach) there was no seperation of cows for C”Y or chalav stam whatsoever. I was to watch the milking, collecting and transferring to and checking of the transport trucks.
It was the SAME COWS for all production runs from the three different farms I supervised.