So the alarm panel is acting as the "CO"? In other words, it is providing 48vDC @ ~23ma or better, and 75-120vAC ringing indication? That is the minimum requirement of a LS port on the 3300 controller.
I am kind with johnp here and wonder if this is the right setup... I have never seen an alarm panel connect to the 3300's LS ports, unless it was for a telco line but went through the alarm panel first (very common).