Honestly just sounds like voxel cone tracing without the cones: https://research.nvidia.com/sites/default/files/publications/GIVoxels-pg2011-authors.pdf
That’s the original paper. Lot of advancements since then, will finally be coming out in a games soon, The Tomorrow Children, though that’s only an approximate, and I highly suspect Deep Down as well. Both PS4 exclusives, as unfortunately the XBO’s bandwidth to ram is quite low except for its fast 32mbs of Esram. Still, it might be possible to do it there too. Regardless, take a look, as produces much more temporally stable results and with the automatic filtering lets you do rough specular for cheaper rather than progressively more expensive.