Yeah... well, maybe... We run Communications Manager 6.1(2).  I'm betting the Serviceability interface hasn't changed that much.  If your FXO ports are on a gateway (such as a 2800 ISR or 3800 ISR), you should be able to log into the Cisco Unified Serviceability interface and navigate to Tools > CDR Analysis and Reporting.  Sign in to CDR Analysis and Reporting then navigate to Device Reports > Gateway > Utilization.  On the left hand side of the screen you'll see all the voice gateway types, select the type hosting the analog ports you want details on (this updates the screen), then select the actual analog ports you want to know about. 

You can get an hour by hour utilization report for one or more analog ports.

This assumes, of course, you're an administrator and see all the CDR Analysis and Reporting options and that you have CDR turned on.