It's a little like if a shipment of guns and rifles makes its way into a city's criminal underworld. Crimes and turf battles get more violent, with more bystanders killed, and the police/private security escalate with their own weapons and crackdowns.
With that said, wands have a lot more utility than guns. So you'd see a lot of those criminals doing jobs they couldn't before, harnessing effects like dimensional jaunt, invisibility, jump.
For how it impacts on the players, it depends what you want. Do you want a random encounter when they come across a pair of thugs battling it out with wands? Do you want to reduce the number of Kell thugs later in the adventure as they have been pulled away to deal with the wand-armed Family? Do you want a session spent post-book where the PCs track down where Gale is storing the bulk of her wands, to capture them?
