Also, we do not know if in all those years, whether or not the trucks or wheel sets were ever switched out for any repair or defect.
While - at present - we don't know that information. NTSB in their investigation will likely be able to ascertain all that information and more from AAR/carrier records. Records that are maintained for just such a investigation.
Re: trending HBD data... The temperatures noted were above ambient. Not actual bearing temperature. Ambient was below freezing, if I recall.
Found this interesting study of bearing temps vs. damage. It is revealing in just how much damage a bearing can have without causing significant temperature rises. Page 17 has conclusion brief, https://www.utrgv.edu/railwaysafety/_files/documents/presentations/jrc2016-5816.pdf And this one has some good operational data and info. https://link.springer.com/article/10.1007/s40534-020-00230-x
