Barely related to this, but looking at the results (section 5.2) I'm amazed at how much worse T-Mobile is for latency. AT&T and Verizon both give about 2 s of delay for Hangouts, while T-Mobile gives 7 s of delay.
The reason T-Mobile looks so bad is because the T-Mobile trace was from a 3G network with very poor conditions, while the others (AT&T and Verizon) were from LTE networks under relatively good conditions. You shouldn't compare the quality of the carriers from our results.
Almost all telecom's network service will vary depending on specific location. Instead of X has better latency than Y, the correct conclusion should be that X has better network _in this particular location_ than Y.
