In the case of Verizon it's not happening when it's 3 AM and no one is using the tower, the whole point is that it only would happen when on a congested tower and only for the duration of the congestion.
So a person who pays for 10GB, and has already used 8GB would not be throttled, while an unlimited customer who hits 5GB would. Exactly how is that tower not congested for the one who has used 8GB, but it for the one that used 5GB? Either the tower is congested, or it is not.