Lifthrasil: they could, theoretically, both be scum
The more I think about this the more likely it seems to me. There is no "theoretically" about it.
One of them lied: there is no doubt about that. And as was pointed out, none of them had a reason lie: as Town they wouldn't lie; as Scum scum!agent had no reason to lie and bring unnecessary attention to himself, and scum!trent could simply have corroborated agent's claim without the attention.
So what happened?
Here is my theory:
Joe didn't reroll all scum. All he did was reroll a single Town to replace micro/dedo (possibly with a minor other role balancing change). So agent thinks of a clever gambit: he'll out his team and claim it's changed because no one would expect scum to do it, right? Only he has no way of communicating it to his buddies, and when trent comes along he thinks "What on earth is that idiot doing??? He's outing us all just like that?" and instead of playing along he decides to bus agent.
So that's where they are now. They can't retract their statements now, so the best they can hope for is that when one of them dies, the other gets good Town points.
I say we lynch trent next even after agent flips Mafia.