I've had a very similiar problem - I wanted to use a ThinkPad S30 keyboard with an arduino nano (or any atmel), and no docs were available.
First things first, you'll need to figure out the keyboard matrix. I'd recommend using a multimeter with a beeper, and touching every single contact together with every other contact on those flex cables. It may be tricky, as you'll need to press every single key in order to know which one is which connections. After getting a beep, note everything - to be exact, which pins were shortened and which key(s) gave you a beep.
Then, you'll need to create a prog that will translate keystrokes from the keyboard to USB HID or PS/2 interface. The testing process will be very, very hard, but I'm sure that with some courage you'll be able to do it. Please post results when you'll finish, I want to see it working :3