dominated by the "favelados" on one side and the megacorps on the other, wich would employ BOPE to fight their battles. Megacorps from Rio would include some of the largest ones in the world: hyper-polluting oil corp Petrobrax (with the name change to show it's now an international player), ecology-damaging mining corp Vale, and political-savvy TBX, which no one quite knows what it does but is owned by Thor Batista, the richest man in the world
Brasilia is already a Cyberpunk city, built of pure concrete in the middle of a red-dust almost-desert called Caatinga. Just make the Brazilian government inept, ineffective and dominated by corrupt congressmen (not that far from the truth)

I hope this helps! Cheers

A:

(Disclaimer: I'm a Brazilian)
Most fictitious representations of Brazil exaggerate on some of thethan Paulistas, however (at least in terms of dealing with player knowledge as opposed to character knowledge). As one of the BRIC economies, there are plenty of reasons why the player characters might decide to seek their fortune in Brazil, such as:

hired as bodyguards by a wealthy family (just like our beloved Max)
working as mercenaries, or for a private military contractor

see the Chrome Berets sourcebook by Thomas M. Kane for military Cyberpunk campaigns

part of an expedition into the Amazon (perhaps a scientific mission, or something more nefarious)
visiting one of Brazil's research institutes, such as the synchrotron

perhaps FAPESP has developed a new type of cybernetics, or an advanced form of netrunning?

security for a major construction project, like Belo Monte
industrial espionage
an arms deal (there are a bunch of arms manufacturers