Good point^. Best thing to do is detach the cable from the caliper, and see if you can move the parking brake actuator. If you can, then as B3NN3TT said, the cable may be frozen. You might be able to try to slide the cable within the jacket to see if it moves at all.
I just did new rear calipers and new rear parking brake cables (Raybestos brand cables, from Rock Auto) because my one of my calipers was shot, and both of my cables were literally freezing. When we had freezing temperatures, moisture/water trapped inside the jacket would freeze up and prevent me from engaging/disengaging the parking brake. Apparently, once the boot on the caliper-end of the cable is destroyed, water gets in, causes rust, and freezes in cold temperatures.