Following instructions from an employee I'd called, I tried it and it worked today. After pressing "intercom" and "page", I was patched in. I only tried it as a test (no prank), because the store is relatively small and it would be pretty risky.
So anyway, if I were to call the store connecting to a department, how could a friend pickup my call? These phones are all around the store (sometimes ringing), but is there something special that would need to be done to get connected to the incoming caller? I'm hoping this store might have their intercom remotely accessible, so that a friend could transfer me in.