I need to double-check, but I think the type of the call is written to the Call History table. If you need the full information, then I guess you could to add a trigger to the CS table for inserts and then use that to copy the information to a second table for audit purposes.
A bigger question, however, is: How far "off" are the callbacks? Are these Agent-Owned, or Campaign-Wide?
What Dialer does, prior to placing a call "for" an agent is to see if they have any scheduled calls "in the past". If so, then it places them immediately. The problem is that if a call is scheduled for, say, 10:00am, and the agent becomes available at, say 9:55, they get another call which may run until, say, 10:10 at which point the scheduled call is "in the past" and placed - 10 minutes late. Is that what you are seeing?