When I say confirmed, I mean that IMDb has added two more voice actors to its SanAn info page. First of which is Shaun Ryder playing the roll of Maccer, as reported by UK tabloid "The Mirror" sometime last month. The other is Sarah Sido, who is just listed as being a voice. While they're generally rather reliable, they have been known to slip up in the past. Only time will tell at this point.
Thanks to PlanetGrandTheftAuto for the heads-up.