Sidenote 1: Yup, Solitary is in the background saluting with a drink and looking at them in the final page when they walk Bizarro out. He`s not seen when they arrive at the scene and technically there wasn`t an angle towards the table he`s seen sitting at in that final page but you can always make a case that they just can`t see him OR he comes and goes as he pleases.
Anyone notice the Arkham Knight callout? "And I said, Screw You, Bat-Freak!" and the Bar sign?
Sidenote 2: Absolutely