It seems the iSense needs more time than you gave it. Whether a remote setpoint change is permanent or temporary is indicated in a DataID 100 message. Looking at other iSense logs it seems that this message is only generated by the iSense around once every 12 minutes. Your log shows such a message at 16:02, so most likely it never occurred between the time you set the override and the scheduled change. This means that at the time of the scheduled change, the iSense may not have known that the remote setpoint override was temporary and apparently it did not apply the scheduled change.
I think you can only draw a definite conclusion after you try the TT command at least 15 minutes before the next scheduled change.
Was the scheduled change actually for 16:00 on the day you tested (24/12)? You indicated that when you manually set a temporary temperature the thermostat showed that it would be in effect until 16:00 25/12/2012, i.e. a day later.