"Countdown With Keith Olbermann" the highly rated cable news program, will be shown on network television on Sunday before a preseason NBC football game between the Philadelphia Eagles and the Pittsburgh Steelers. Since Mr. Olbermann, right, will have a regular role in NBC’s football coverage once the season begins — appearing as a co-host on the pregame show "Football Night in America" on Sundays — this weekend’s appearance of his cable show will give a wider audience a look at what he has been up for the last four years.