In looking for incidents on the C&C/SPng I found the newspapers to be a good source.
Only one incident (with 2 fatalities) in 1915 has an ICC report; and that was because a couple of ICC inspectors were in Mina at the time. They quote various SP officials in the report.
From reading the Mina newspaper, it seems the company investigated most incidents --even a flat car (apparently overloaded) that came apart in a train. The editor of the weekly paper was at times the non-employee on the inquiry team. The editor published a number of these findings.
But, as of yet no actual report or finding has come to light of the incident on July 3, 1924, that had the two 4-4-0s pile up in a cut just down from the summit. One of the firemen had traumatic amputation of both feet and he died on the operating table getting revision surgery.
Brian Norden