Nope, they physically open your packets, change the content of the HTML, and send the packets along the way.
Even if you access the IP directly, it still injects code via MITM attack.
I saw the MITM injection from Comcast exactly once and it served as a reminder to go and change the DNS settings on my routers. Never seen the injection since, and I've been on Comcast for years.
Maybe you're right and me not seeing injections could be explained that a lot more traffic goes through SSL/TLS by default, or I'm just not getting close to my monthly quotas any more.
