Never tried to audit that particular file, but have come across others which are only accessible as true root. I suspect that this is the case for this file. You likely have only 3 choices to get the information:

1. Your current solution of setting a cron job to cat the contents of the file to another file and gathering that. Keep in mind that auditors will not be wild about that option because it is not the original file and you lose the chain of custody along the way.
2. Install the agent on the box as true root so it can access all of these files.
3. Provide true root credentials to the cred_db and then gather the data. This is the least likely to be acceptible to the Unix admins, although they may buy into it if they get to enter the creds themselves. The challenge there is to have to re-enter the creds every time they change a password.

In my experience, if that level of reporting is required on such sensitive files, I would recommend option 2.

Chris Tyrrell
Compliance Practice Lead
Conventus Corporation