The Jan 2012 Trains has a pic (pg 73) of a BNSF car knocker repairing a "catwalk on an old boxcar...in 2010". Two questions: 1) I never heard them called anything but a running board. Were they ever referred to as catwalks, or is this a modern misinterpretation akin to calling a steam locomotive a "unit"? 2) Considering they've not been used for 50+ years, why the heck would BNSF be repairing/replacing (and a wooden one, no less)?
First, remember that terms not used in many years fall out of people's working vocabularies.
As far as why, might there be a chance Mr Buffett's mechanics are assisting a museum restoration?