I started experimenting with this idea. I have WP8 files extracted from a firmware file. I copied these files to my surface RT. I was able to run some WP8 applications out of the box. however, applications that require UIXmobile.dll (WP GUI) failed to run. Now both WP8 and W8 share the NT core. so some libraries would just work. now the main WP8 library UIXmobile.dll doesn't work out of the box. as it uses a different function to create the gui for its applications.
I was thinking of something similar to what has been done by "mamaich", to implement a library that will replace the WP8 call wtith the standard W8 call (for example: use createProcess instead of createApplication) and pass the common calls to the already implemented APIs.
sadly , It's a very difficult task for me to do. I'll be spending time on it but i can't promise of any fast results.
I'd like to thank the authors of these threads for their wonderful work:
1. Running x86 apps on WinRT devices (by mamaich)
2. RT Jailbreak Tool (By netham45 )
3. Desktop apps ported to Windows RT (by GoodDayToDie)
4. (FFU) ImgMount Tool v.1.0.15 (by AnDim)