Well, Sony made an *almost* perfect ps1 emulator to run on the new Sony Tablet. When you have the full documentation, it isnt about how long is it going to take or how hard it will be to get it right. Its just about how much power will you need to run it fullspeed.
Cause Low level emulation (which is most accurate and most straght forward if you have the docs) is usually slower. Still, I suspect they will be HLEing ps1 on their tablet, as weird as it may sound, unless they want to give people a free copy of the ps1 BIOS with each device. But that also means they would have to do some new research on it, like they were reverse engeneering their own system :p
weird.