Via the AXL APIs...no.
For real-time call information you will want to investigate the CTI APIs: TAPI and JTAPI
http://developer.cisco.com/web/tapi/home
http://developer.cisco.com/web/jtapi/home
Another possibility, if the customer is using Cisco Unified Presence integrated with Cisco Unified Communications Manager to monitor phone status as a presence indicator, is to use the CUP presence APIs to get busy/free status. There are REST/SOAP APIs for CUP, though note these are user-oriented, rather than device or line oriented.
http://developer.cisco.com/web/cupapi