You need to do two things. First, you need to get the cage to play the shut down animation:
AssignCommand(oCage, ActionPlayAnimation(202, 1.0, 0.0));
Second, you need to destroy the invisible placeable that blocks you from entering or exiting the cage:
DestroyObject(oCageBlocker, 0.0, 0, 0.0, 0)
The tags vary, so you'll have to look them up.