Hi,
The best solution would be to use traffic reports from ld 2. If you read that section of the NTP's you will find that you can set hourly reports to be generated for either network loops or, what would be better, route's. The only catch is that the PABX generates the report and outputs it to a tty, once that is done the report is reset, thus you require a pc to catch the reports. Have a play in ld 2 and see if it helps.
Cheers