A small article titled Artists make tracks to 'Tomb'
located in the "Music" section of usatoday.com
contains a tidbit mentioning NIN's contribution to the "Tomb Raider" soundtrack. Here's the little bit concerning Trent/NIN:
Nine Inch Nails' Trent Reznor, a longtime video-game addict, screened several scenes before writing and performing Deep, slated for a mid-May release as the second single.
...and a thought from the producer of the soundtrack:
"We needed songs that worked thematically and captured the high-intensity vibe and darkness," says soundtrack producer John Kirkpatrick of Elektra.
Also, rumored to appear on the soundtrack is a Danny Lohner remix by A Perfect Circle
(who accompanied NIN on their Fragility tour) according to the APC mailing list.