Maya will have been used for modelling and animation, however as Zielak says, a lot of the visual effect and material work was all done inside UE4. You can see some discussion of the Visual Effects in cascade here: Infiltrator Breakdown: Visual Effects | 01 | Feature Highlight | Unreal Engine - YouTube
If you’re specifically interested in artist workflows, there’s an in depth look here: Intro for Artists | Live Training | Unreal Engine - YouTube.