Arkham City IncidentAfter the assassin disapear, Batman scans the memory of the guardians and we know that the entrance is hidden in a wall. During Protocol 10 the guardians were gathered up in a pile.
Harley Quinn's Revenge Incident
Harley Quinn acquired the Guardians and used them as her henchmen in the DLC package. After Batman was saved by Robin, Harley unleashed them against Batman, but also took a sniping position on her Joker memorial to help in killing him. It should also be known that Harley painted them to look like Joker.