No, this is not possible. There is always only 1 instance of the SEPmac.cnf.xml file on the tftp servers. This instance will reflect the latest configuration of the device.
If you really want to track this, then there's another way of doing it.
1. Schedule a job on a linux server to pull all cnf.xml files from the CUCM TFTP server. This script should read the names of the files from a different file.
2. Compare files with the same name with an older file already existing on the linux server. If there are changes, record the changes, else just replace the older file.
If you want to track configuration changes on the CCMAdmin page (which includes changing phone confguration, and hence changing cnf.xml files as well), enable the Audit logs and collect them at regular intervals so you can see when the change was made.
http://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/service/7_1_2/admin/Serviceability/saaulog.html
