Fax Pro Question

If I am a user linked to a primary extension in freepbx 13, when I send a fax, must it be sent through that primary extension / did? We use separate lines for voice and fax, and I want users to be able to get their voice mails etc from their primary linked extension in UCP, but also be able to see all fax info from the fax extension in UCP, but have the faxes actually sent and received on their fax extension, not their primary extension. Is that possible?