How is possible? PS4 and XBOX ONE are based on AMD.
NVidia has been busily optimizing and porting PhysX and other Gamesworks programs to x86-64 and DirectCompute for quite some time now, which opens other platforms up to these technologies..
The latest Metro Redux games are a perfect example. They updated the PhysX SDK from 2.8 to 3.3, which gave it a
MASSIVE boost in performance when running Advanced PhysX on the CPU. I've tested it personally. Provided you have a strong CPU like a Core i7 (preferably overclocked), you can enable the Advanced PhysX effects without any significant performance hit. Before the upgrade to PhysX SDK 3.3, running the Advanced PhysX option on the CPU would result in a massive hit to the frame rate no matter how powerful your CPU was.
This did require some sacrifice however. Some of the interactivity was scaled back, but the overall quality was not diminished.. Interactivity typically requires a lot more processing power, and is more naturally suited to hardware acceleration..
As for the consoles, the planning of the incorporation of advanced PhysX effects says to me that NVidia will be exploiting their compute capabilities. The consoles were always meant to use the compute units for heavy processing, as their CPUs are very weak...