Here's a short list of track (not drivers') frequencies from yahoogroups about a year ago, with comments from the people who posted them:
3. 464.050 DPL 116 - Race Operation (seems to be the "main" channel)
4. 461.9625 - Used by race officials who line up the cars prior to a race
5. 464.2375 - - Used by race control to discuss issues they don't want all the crews to hear.
6. 464.6625 Security
9. (unk) - PR & marketing
16. 451.175 Emer back chan. "They think that this is a private frequency. They use it to discuss sensitive info, driver injury, etc."