I probably spent close to an hour dicking around in the photo mode looking at how they handled the flashlight GI. The long and the short of it is that it's similar to the Last of Us solution, which is basically to do a raycast/line trace from the flashlight and then place a point light in the location where the ray hits and tint its color based on the albedo of the surface underneath.
By and large the flashlight is used in stone areas with very rough surfaces without strong specular highlights, but in the few areas where you can get a highlight, it's possible to see evidence of the bounced lighting being cast by a single pointlight.
Actually, to clarify as well, it's not strictly an omni-directional pointlight, but either a spotlight with a 180 degree cone angle, or a pointlight with a light function that darkens most of the back half. I have some shots I'll have to pull up later, but you can find some areas where there are boxes with sharp right angle corners, and you can see how the bounce light takes the normal angle of the surface it hits and casts light in the opposite direction.
Regarding their volumetric lighting, they have somewhere between 3 and 5 different types of volumetric light shaft tech that are used in various scenarios. Some of them are old school and completely faked (basic mesh with a fog-like material with falloff), others are screenspace fakes (you have to face the light source, and then it blurs the light toward the camera, using the depth buffer to cut out shadow shapes), while some are the most accurate (and probably expensive) and capable of coming from off screen while still performing dynamic occlusion to cut out shadow shapes.
Something related that I was also looking at is their volumetric shadows in water surfaces in the first few areas of Madagascar and later when you have control of the boat in the clear turquoise water. It appears they're using the same tech or principles behind their volumetric lights to create volumetric shadows in the water. In the case of the turquoise water, they did cap off the maximum depth of the effect, so the volumetric shadows only penetrate the water by a meter or so.