They also leverage their 'network' of wifi hotspots (which are just all the home routers they give to cable customers). Either way I imagine they route all the traffic through a gateway on their network so are likely to have just as much opportunity to collect data and/or modify traffic as the tower operator would.
That's a good question, but I have a hunch and am willing to bet that by sheer coincidence they will focus particularly on the smallest of the seven named.