While I am no fan of AT&T (I am a current subscriber with sub-optimal performance and would switch to almost anyone else, if given the chance), I am well enough informed that I have no real issues with this sponsorship. The short sponsor spot at the beginning of CITA coverage is short and very blunt; Linus isn't going out of his way to make them seem great. Luke's coverage of AT&T Drive was well done as too, it was more a -this would be kinda cool- video about the tech, and if they removed the branding could easily have been applied to any other company offering similar services.
In the end I trust everyone at LMG to give an honest review and I don't see them bending over backwards to comply with a sponsor they don't like. If Linus felt they'd be compromised, he would have passed on the deal.