I guess, the softphone can be used in data vlan also. A very similar configuration of voice and data vlans is discussed along with the configurations in the following document. You could check out this with your configurations.
Configuring and Troubleshooting Cisco IOS Telephony Service (ITS)
Are you firewalling your Call Manager cluster? The recommended security setup will block access from your data vlans to your Call manager. Other than that it should work, except for QOS issues. This assumes you don't have any basic routing problems.
No, I'm not firewalling the CM's. In fact, the CM cluster isn't even on the voice vlan...the CM's are at another site, and we connect to it over a T1 link. Configs for both the data and voice vlans are the same.
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.