I have successfully flashed one Thinkpad T60 with Libreboot. It is currently in my locker.
Using precompiled binaries from https://libreboot.org/ seems to work. Self compiled coreboot binaries would lock up on boot.
Buspirate is quite shit for flashing the spi flash on the motherboard because of the slow usb-uart speed. Raspberry Pi worked very well.
It is quite pain in the ass to get access to T60 bios chip so i soldered some jumper cables on to the board for easy access.