The Sefer 1מענה לאגרות (page 221) argues on R. Moshe Feinshtein's leniency allowing industrially produced milk to not be watched by a Jew during the milking. His basic argument is that the Ramo says in Shulchan Aruch (Y.D. 115) that if a Jew walks in after the milking started, since nowadays non-Kosher milk isn't found at all, it can be permitted. The Shach and the Taz take it even further, that this only applies if the cow belongs to the Jew.
So his question (nicely restated) seems to be: If a non-Jewish worker, working for a Jew and for the Jew's milk with the Jew's cow, still needs to be actually watched at least most of the time even though he has no financial incentive to improve the milk supply, how is that different than industrial milk production that we should say that a Jew doesn't need to see it at all? Even the Ramo seems to require some direct supervision, even if he is allowing the cow to be owned by the non-Jew.
I'm wondering what answers are proposed to that question?
1 - A very controversial book in its time (1973). The purpose of it was to argue with R. Moshe Feinshtein's Teshuvos which were, in the author's opinion, too lenient. The author uses very nasty language (lies, ignorant words, etc.) against its target, and thus while it's content is viewed as making some good points, its language against its antagonist was regarded as unacceptable and thus the book widely ignored.