I forgot to mention this. Part of the reason for me thinking the environment uses static shadow maps is that these environment shadows not only blend with actor shadows but they are also projected onto the actors themselves, making it look like everything is part of the "same world", belonging together.
I've taken some snapshots to illustrate (pardon the low resolution).
• Here the actor's shadow is merging with static environment shadows.
• Here you can see how the environment shadows are pixelated, and how they're projected onto the actor.
• Look at that partially lit seat, centered of the screen. The shadow projected on it is very pixelated, and comes from the environment. When you approach the seat, this shadow suddenly gains a higher resolution.
• In some parts of the levels such as behind large buildings (places where the actors are always covered in shadow) it's easier to notice that not only are there shadow maps involved but also some sort of baked AO term - you can see this below the car and below that ledge on the gray building to the left.
Aditionally, in these cases the actors do cast dynamic shadows (even darkening the environment shadows), but then they're not hard edged like when under then sun.
Instead they're very blurred up to the point of being smooth and they're made almost transparent, looking like a subtle shade.