The System Event log contains an event for every time an authorization is successful (event id: 1). One can query for Quarantine-State attribute for these events to determine the health status.
If SQL Server based Accounting log is set-up, then querying the SQL Server as per http://www.microsoft.com/downloads/details.aspx?FamilyId=6E4357F7-4070-4902-95F1-3AD411D963B2&displaylang=en (with an additional column specification [page 15] as: MS_Quarantine_State and corresponding WITH clause: “MS_Quaratntine_State ‘int ./MS-Quarantine-State’) will also give the health evaluation state determined by NPS.
If NPS is configured to Local File Accounting instead of using an SQL Server (in IAS format, rather than Database-compatible format), then also it is possible to process the text file for health status; I still need to look into the exact format details.
Thanks,
Sreenivas