Gaon
“Rav Moshe agrees that according to many poskim (Chasam Sofer, Pri Chadash) it is still considered Chalav Akum”
this isnt correct. The Pri chadash holds that if we know that the milk is Kosher (for example only cows are around) there is no reason for a Jew to observe the milking and there is no issur or Chalav Akum. The vast majority of Poskim (including the chasam Sofer) do not hold this way and require a Jew to observe the milking.
R’ Mohse notes that we do not hold like te above mentioned Pri Chadash, and yet the government watching is as if we are watching and even according to the vast majority who require a Jew to watch in all cases, the government is ok.
Of course others argue on R’ Moshe which would make the milk Chalav Akum ie treif.
In summary, regaridng milk in the US (what R’ Moshe calls “Chalav Hacompanies”
Acc PRi Chadash – Mutar the gezeira of Chalav akum doesnt apply. (This isnt accepted lehalacha)
Acc R’ Moshe – (Acccording to everybody other than Pri Chadash) Mutar – It is considered Chalav Yisroel (though bal nefesh yachmir)
Acc to those who argue on R’ Moshe – Assur it is Chaluv Akum ie treif