Is it possible to transfer an active call from a PLAR line to another extension? CUCM 9.1

Question

We have multiple PLAR's set up that work great but not everyone has them on their phone. So the problem arises when someone who does not have a certain PLAR on their phone and wants to join the conversation. We had hoped that we could transfer/conference the call on the PLAR to the extension of the person who does not have it on their phone but get a busy tone as soon as the transfer key is pressed. Is this at all possible?

Answer 1

I am going to assume that you provisioned PLAR by using a "null" translation pattern (i.e. pattern with no digits). And that the phones will automatically connect to the PLAR destination when they go off hook. 
When you try to do a transfer, the CUCM digit analysis process will use the same CSS logic as it does for a standard/direct call. So, the behavior you are observing is expected. You can't use a PLAR line as if it was a regular phone line. 
Your scenario has sparked my curiosity. In my experience, PLAR lines are usually added to common area phones outside of a secure area or something similar. It sounds like you are using PLAR as secondary lines on user stations. I may be mis-interpreting your scenario but I am inclined to think that you may be better served by using other UCM features. More information about your requirements would be needed to give you proper guidance. 
If interested then please share more info. Otherwise, the answer to your original question concerning PLAR is that it doesn't work the way you want it too.
HTH
-Bill (@ucguerrilla)
http://ucguerrilla.com