BTW, the OU calls it Chalav Stam. Also, in this article, they admit that it’s no longer R’ Moshe’s heter, but a different one (based on R’ Moshe’s heter). Not everyone agrees to it.
http://www.hebrewbooks.org/pdfpager.aspx?req=53256&st=&pgnum=84
This is a misconception. Rav Moshe always allowed milk from dairies even without regulation by the farms (See Igros Moshe YD 1:49 for the concept of “Shelo Ba Lyad Yisrael)
Some say there used to be chemical testing by the dairy that was able to identify the species of the animal the milk came from. If that is true, that was never needed. Also, the dairies used to have on site farms, where the inspectors can see the animals themselves.
That is what has basically changed. The daires are generally not connected to the farms, but understand that acc. to Rav Moshe they never needed to be.
We do not really need a new heter. Rav Moshe never maintained that the dairy inspectors had to figure out if the milk is from a cow or not. Rather, they had to make sure no non-kosher milk was added in.
Today, the heter is only stronger than before. Besides the FDA at the dairy, there are state inspectors at the farms.