Hi it is possible.
Using command KSMDI, you can set another extension to monitor this extension and pick up the calls.
KSMDI:dir=yyy,mdn=xxx,dig=xxx,key=??;
DIR: another phone to pickup user1 phone
MDN and DIG is the extension to be monitored. (User1)
key: any unused key on your digital phone. When the monitored extension rings, this key will blink and you can pickup the call by pressing this key.