Season 4 (the odd-numbered missions) is basically what happened in Seattle, and Storm Front pretty much recapped it all and then some.
As you probably know Knight Errant took over from Lone Star and got rid of the Mayan Cutter. Half a year later a copycat killed Bull's daughter and others, turned out he got hired to off important Ork-right people and throw in some distractions, Bull had the guy hunted down by runners and his wife pulled the final trigger.
Furthermore someone (Humanis/Alamos? I never got to play the original Ashes, unfortunately) bombed the Underground. Then, a few months later, a political campaign (Prop 23) got started to have the Ork Underground recognized as official district. Needless to say the Governor HEAVILY opposed this. The racist scumbag.
During that campaign a council-member (senator? can't recall) was noticed in the middle of the Humanis peeps at a double demonstration. Later, Bull managed to chase down the guy who hired the copycat killer, though he and his club got blown up in the process, he himself barely survived. The D.A. office got exterminated by an Assistant District Attorney working together with a Skraacha (Ork Underground gang) leader who both opposed Prop 23. They got busted and the only other surviving A.D.A. became Acting District Attorney. This ADA is Dana Oaks, who opposed the Ork Underground since she hates criminals, not because of racism.
The Ork Underground got firebombed a few more times in a short while, to pretend the OU is unstable and shouldn't be recognized as official district. The ones responsible were hunted down and their heads exploded due to cortex bombs. Their boss took more time to hunt down, and as it turned out near election day, he was working for the Governor and decided things like this would be a good way to help. Turns out he's the guy who, while drunk, gave a mate of his the Copycat Killer idea, was responsible for the recent bombings iirc, oh and the Governor's aide (the man behind the throne) wants him dead. He went missing and it turns out the Redmond dragon Urubia has him.
(Did I mention Dana Oaks, before Prop 23 reared its head, was looking for a way to take down Urubia for her crime-dealing? And now Urubia has Jeffries, who she needs...)
Anyway, Prop 23 barely passed and while Brackhaven forced recounts, finally a federal judge told him to **** himself. Meanwhile, Bull and Dana Oaks, now unwilling partners of sorts, have dug up a LOT of dirt on Brackhaven. An FBI agent dug up stuff himself and helped make Dana Oaks permanent District Attorney, but he went missing when he was coming to town with all the dirt he has. In Splintered State he surfaces and the evidence ends up in one of the interested parties' hands. It's not an adventure I advise to an inexperienced Shadowrun GM, though. The toughness and loot amounts are off the charts there.
Anyway: Dana Oaks managed to put together a grand jury and Detective Tosh Athack and his Black Knights motley crew keep her alive, while Brackhaven is getting re-elected but the Grand Jury is hanging over his head like a sword of Damocles. Meanwhile in 2075, the Ork Underground got blown up AGAIN (Ashes 2.0 in Sprawl Wilds) in an attempt to put the Underground in a bad light.
There's two events here that don't have their outcome in the official canon yet: Splintered State and Ashes 2.0. However, if I were you I'd assume the dirt comes out pro-Underground there, though you don't really have to mention it. Basically, the Ork Underground is official now and the Skraacha are begrudgingly working together with Knight Errant somewhat (though there's still plenty of crime in the OU), with KE mostly letting the Skraacha handle things because that's cheaper. Brackhaven has gotten re-elected but he's hanging by a thread and well on the way to lose Corp-support and the man behind the throne is preparing to cut his losses. Bull is NOT attempting to become mayor of the Underground, as much as I+CanRay like pretending he is, but he has become a big person in the efforts to improve its public image and the secret war to take Brackhaven down.
As for Oaks, she's trying to get the wheels grinding but it will go slowly against Brackhaven. However, she still has other things to fry, such as Underground crime and Urubia. Especially since Urubia has/had Jeffries and only Spirit knows what the lady wants for him... She's a good tie-in to any runs that involve getting intel+targets KE can't really reach in the law's hands, using Tosh to arrange the dirty work.