The Cisco Jabber file can be uploaded to CUCM Publisher that is acting as TFTP server, upload the file with your <StartCallWithVideo>false</StartCallWithVideo> setting and restart the TFTP service and browse the file in IE or Chrome at http://X.X.X.X...
Simply you can do it without the config file , in call manager , go to the Enterprise Parameter, Under cisco jabber, the setting never start call with video always , set it to true , i just did that today in one of my deployments and worked just fine
Reset Cisco Jabber client , if not working add Never start calls with video setting to Jabber configuration file and set it to false or disable this in the Jabber client settings
