Unfortunately you can't if you look at the instructions for 3rd party SIP phones they state you need to create an End User.
You'll need to create them in AD so they sync with CUCM and then use them.
Configuring Non-Cisco SIP Phones
http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/admin/7_1_2/ccmcfg/b09sip3p.html
Step 3 | Configure the end user that will be the Digest User. |
HTH
java
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www.cisco.com/go/pdihelpdesk
HTH
java
if this helps, please rate