Spot, like other retailers, uses third-party workers as a way to insulate themselves from these types of dust-ups. This way they can plead ignorance, point to the cleaning company as 'the villain' & simply walk away from trouble. They look good to the public by terminating their contract with the 'bad guys' while privately negotiating a cheaper deal with someone else.
Since the other crew cleans corp's offices - which are a little closer to the top - they'll give better pay & perks.
After all, I'm sure their offices look a d@mn sight better than the typical store.