So the cell's unique attributes proved useless to the PS3?
And keep in mind that nobody is saying that these things somehow make the XB1 just as powerful as the PS4, or somehow more powerful. It isn't even being suggested that it significantly closes some performance gap. All that's being said is that it's a possibility that Microsoft aren't as clueless as some think and specifically made sure the XB1 was pretty well architected to take advantage of things that they expect to be a major part of game engines and content creation pipelines going forward.
The XB1 looks purpose built around tiled resources, and tiled resources also has strong benefits to shadows without the cost associated with those improved shadows. The presentation from Build regarding tiled resources specifically talks about how it allows ultra high-density shadow buffers, and Microsoft showcased a video demo example of it in action.
Page 38.of the following presentation.
http://www.google.com/url?sa=t&rct=...=xp5uIWa73_tER6TCFk5pkw&bvm=bv.52434380,d.dmg
The full presentation video - skip to 22::34 The demo is also shown on how tiled resources improves shadow mapping.
http://channel9.msdn.com/Events/Build/2013/4-063
If the XB1 is really specialty built for tiled resources, then this is also something that will improve as a result of some of the custom work MS did. Keep in mind I'm not referring to only the XB1 supporting PRT. I'm specifically talking about the tiled resources feature as exposed in Microsoft's API, and how the XB1 seems almost entirely customized with it in mind. 32MB of ESRAM looks a lot bigger when you realize how much data tiled resources allows to be utilized using a tiny amount of physical memory space.
Page 49 of the presentation, where they talk about the Granite runtime overview, one of the middlewares that will support tiled resources, it stresses both residency analysis and decompression. One of the XB1 specific Directx enhancements according to Microsoft's dev conf presentation is ESRAM residency control, and one of the 4 move engines has its own dedicated decompression hardware. All 4 move engines are also capable of tiling and untiling, another important factor in tiled resources.