[continued..] You can't generalize, but you can assume. Quite likely many Thinkpads use the same piece of code to handle firmware password-checking. Once the code is changed, it'll likely propagate (slowly) inside the company to all of the new (or firmware-updated) laptops.

That being said, it's likely the firmware's failsafe-mechanism kicking in when it cannot access the memory chip that stores the password (because access to the chip is hindered).

Yet utilizing the "WP" (write protect) pin on the memory chip ought to do nothing in my opinion - unless the firmware tries to store something to the memory at boot time (which is entirely possible). On the other hand, forcing clock or data pins to ground - in effect disallowing any signalling via them - should be a sureproof way to force the firmware to trigger it's failsafe mechanism.