This headline is misleading. We don't yet know what caused the crash, so it's a leap to say PTC could have prevented it. We do know that the train was traveling at a high rate of speed but not the reasons why it was doing that. If it was a systems failure then it's entirely possible that PTC would have been irrelevant. This is just like the rush to judgment against the engineer, who everyone was ready to lynch after the accident; all we know for sure about him at this juncture is his cell phone was turned off and his drug/alcohol test came back clean.
Do some reading about PTC when you have a few minutes; like most Federal mandates it was:
1) Unfunded.
2) Ignored existing technology that could do the job nearly as well for a fraction of the cost.
3) Ineffective, in that there have only been two train accounts in the last 20 years (three if this one is confirmed) that it would have prevented.