Page 2, Panel 3 - Dr Mid-Nite: "I did a residency under Chuck McNider". By this comment, it's apparent that the latest Dr Mid-Nite met the original, though this story is yet to be told in a comic.
Page 3, Panel 2 - Other non-doctor types that Black Canary may have come across? Dr Fate (former JSAer and JLAer - Kent Nelson), Dr Destiny (JLA villain) and Dr Light III (former JLAer). Both the original Dr Fate and the third (and the only heroic) Dr Light were founding members of the Giffen era Justice League, along with Black Canary herself. Furthermore, since Black Canary was retconned to be a founding member of the original JLA, she therefore would've fought Dr Light II in Justice League of America #12. Note of interest: The original (golden age) Dr Light was an enemy of the original Dr Mid-Nite (Thanks to Graeme, for all the Dr Light info!)
Page 3, Panel 5 - Mention of Oracle, Black Canary's partner in Birds of Prey, by Chuck Dixon.
Page 8, Panel 2 - The other speedsters seen here are Johnny Quick (former member of the All-Star Squadron, and also seen in the 1992 JSA series), Barry Allen (the Silver Age Flash, who died during the Crisis on Infinite Earths), and Wally West, the current Flash, who was recently presumed dead.
Page 8, Panel 3 - Does this scene imply that Hawkgirl killed a man in the past, or will, in the future? We do know that she had a checkered past, according to Mr Bones (#6)..........
Page 9, Panel 2 - The Hawk-creatures here represent Hector's lost parents - Hawkman I and Hawkgirl 1.
Page 12, Panel 2 - Rose/Thorn, mother of Obsidian and Jade, had her death revealed in Infinity Inc Annual #1.
Page 14, Panel 3 - Note the minor spelling mistake: instead of "Doctor Midnight", it should be "Dr Mid-Nite."