I think you are confusing Fox Broadcasting Company with the cable Fox News Channel. Fox Broadcasting could only show it live on the East coast as the speech is at 8pm EDT(Fox's primetime is 8-10pm). Fox Broadcasting is scheduled to show repeats of "Trading Spouses" & "House, M.D.". G.W. is lucky it is repeat season, otherwise the "Big 3" probably wouldn't have covered it live either.
I am not confusing anything. Both the Fox News cable channel AND the Fox Broadcasting Company is pre-empting programming to carry the speech live.