Even lowly NBC is not above schedule shifting to try and blunt the competition's ratings, as NBC is moving Biggest Loser's start time to 9pm on February 2, to go head to head against the premiere of the final season of Lost. A repeat Biggest Loser will air at 8pm, and one fewer Jay Leno Show will see the air before it expires.
I'm not sure how much audience overlap there is, but good for NBC for at least being aggressive.
Update: Robert brings up a very good point in the comments. This might have been done far less as a challenge to Lost than an effort to spare Biggest Loser from any American Idol competition, particularly since NBC cares nothing about The Jay Leno Show at this point.