When Oliver and Felicity are discussing her new code name (Overwatch), Oliver mentions that he thought of giving her the name "Oracle", before stating that it was taken. This is a reference to Barbara Gordon, who took the name "Oracle" after suffering a similar fate in the Batman comic "The Killing Joke" as Felicity does in the show.
Oracle, the Huntress (played in earlier seasons by Jessica De Gouw), and Dinah Lance/Black Canary (the comic book character on whom Laurel is based) were the lead characters in the short-lived television series Birds of Prey (2002). And instead of being the daughter of a mob boss, Huntress is the daughter of Batman and Catwoman.
Oliver states that the codename "Oracle" is taken, indicating that he is aware of the existence of Barbara Gordon and the Bat Family. However, in the Elseworlds crossover event, Oliver tells Barry and Kara that he doesn't believe Batman exists. It's possible Oracle, as in many of the versions in the comics, communicates with other vigilantes and groups completely separate from any Bats and without necessarily revealing her connection to them.
The villain of the episode, Lieutenant Joyner, is named after the creator of Shadowspire in the comics, Tom Joyner, who also created the hero Damage, AKA Grant Emerson, mentioned in the Flash episode Power Outage.