How T-Mobile's video streaming works

How can T-Mobile afford to offer its Binge On streaming video service at no extra cost to its Simple Choice customers who pay for more than 3GB of LTE data a month?
Won't it be crummy video? Won't it cause congestion on T-Mobile's networks and lead to frustrations for customers?
T-Mobile officials offered a few technical details after Tuesday's announcementto shed light on how it will make video streaming from 24 content providers possible starting Sunday.What about the quality?T-Mobile called