jphone,
When I lived in an out-of-town community, c”y milk was trucked in to the local chain supermarket every two weeks. The milk was brought it from a city several hours away in the central US. Although some people chose to freeze the milk to help it last longer, not everyone did so. During the brief time that we bought this milk, we did not freeze it, and yet it did not spoile before the next delivery. (Because c”y milk was so expensive–about double the price of cholov stam–we used powdered c”y milk for about a year before switching to cholov stam). The milk was bottled in plastic containers.
Nevertheless, the c”y I used to buy here in my NYC area community, where milk deliveries are much more frequent, spoiled quickly, whether I bought it at a heimishe store or chain supermarket. Based on my experiences, I must conclude that the spoilage problems with c”y are not due to the containers or the handling in the store, but maybe to storage/ refrigeration problems earlier in the process.