I worked for a Comcast subsidiary in 2010-2011 timeframe. The company owned the network end to end. They had about 250k subscribers at the time across 4 states and at the time was the first DOCIS 3.0 network in the US. They were collecting DNS log data back then. I've been told that hasn't stopped and has progressed. Don't trust your ISP to not be passively monitoring. This particular ISP had closets full of old Sandvines [0] hardware as well that I ran across one day. I asked what the hardware had been used for and the answer was simply: "network monitoring for law enforcement". At the time all of that old gear had been decomm'd. But as I've said in older posts the DC had a hands off, tamper taped mobile rack that was plugged into core routing installed by a 3 letter agency while I was employed. This was pre-Snowden and post 9/11, likely courtesy of all those fun programs we found out about that Clapper denied.

[0] https://en.m.wikipedia.org/wiki/Sandvine