According to a second update from the NTSB on its investigation into the Amtrak derailment, the train engineer wasn’t using his cell phone while operating the train

As part of its investigation into the Amtrak train accident that killed 8 and injured more than 200 people, the National Transportation Safety Board thoroughly analysed the engineer’s cell phone calls, texts, data and cell phone tower transmission activity records from the phone carrier; and records from Amtrak’s on-board Wi-Fi system. This analysis indicates that the engineer was not using his cell phone while operating the train.  Read the NTSB press release