Wouldn't be surprised. While searching him on Youtube I even stumbled on Peter Serafinowicz's appearance on Stephen Colbert where they're talking about him even doing 'bad lip reading' videos for trump in different personalities, one of them being 'Sassy Trump', so he might have had something to do with this show coming about in general.
I don't think he's doing the voice for Sassy Justice, though. That sounds more like Trey Parker to me. But they probably brought him in to do Michael Caine.
I think you need to listen. There's little differences between Peter Serafinowicz as Fred Sassy and Trey Parker as Al Gore. There's tiny little mistakes in the voice. I think you need to watch it again, but this time watch with your ears. </s>
I don't think he's doing the voice for Sassy Justice, though. That sounds more like Trey Parker to me. But they probably brought him in to do Michael Caine.
https://youtu.be/Oe28UOFNlxk?t=138