Dynamic objects are lit by the irradiance volumes that get calculated. Voxelized objects also get lit the same way. Its just that voxelized objects can contribute to the GI calculation. It depends on how complex the part of the scene is changing. Somewhere between 0.5-2ms on a 660GTX to revoxelize a chunk. Chunk size should be (64 * voxel scale)^3, I might attually store them in smaller chunks though, That way if a smaller area changes it doesn't have to revoxelize such a large area.