Warming the camera and the tape is required with the Varicam as well. Unlike the JVC, the Varicam automatically detects tape temperature and prevents the camera from recording if the tape is too cold.
During my first shoot with a Varicam I freaked out because the camera stopped working half way through the shoot. It simply wouldn't record anymore. After a call to Panasonic they asked me if my tapes were the same temperature as the camera. They weren't. My tapes were in the car and it was pretty cold outside. I had to have a PA sit on them while we waited.
I suppose that'll be a new job to add to standard MPAA film credits. Tape Chicken.