Comcast contracted with a third party company to scan resumes and setup interviews. All communication I had was with an external HR rep. The rep set up the interview for me two weeks after I submitted my application online. The process was a bit messy since their auto generated system sent an email stating it was an ins-store role, but turns out that was wrong.
My interview was in an off site building that Comcast rents. It was a panel interview with Comcast's internal HR rep and what would have been my supervisor. I arrived 30 minutes early and sat in the waiting area. Eventually I was led to another floor and into a small conference room which had a great panoramic view of the city.
They asked for my resume to make sure it was the one I submitted, fortunately I had printed two copies and the the original job listing. Right off the bat they asked me what role I was applying for and I touted off the bullet points they had on their job listing. I was corrected and they mentioned that they didn't know if they wanted to continue on with the interview or not as what I read off my paper was not what they were looking for even though the job matched what their records had. It was just data entry ensuring project requests were completed by acting as a liaison. I backpedaled and managed to continue on with the interview, but at that point I knew they already made up their minds and it became a formality. I'm glad I went for the experience albeit I knew the outcome after I left. All in all, despite the hiccups and miscommunication it was very professional, I actually got very positive feedback despite my experience on how I interviewed and was recommended for other positions.
Things to do:
WEAR A SUIT! It's an extremely professional corporate environment and if you don't you will get odd looks.
READ THE DESCRIPTION of the job super carefully and ask a boat load of questions on what the bullet points mean from HR, employees, or anyone who has any concrete knowledge about the job. It'll save you a lot of headaches and frustration.
Expect a lot of behavioral questions and answer in the detail based off the STAR format (google it)