Since you know rail communications thoroughly, I am pinging you for your thoughts on this tragedy.
The revelation that the engineer was sending a text message is likely to ensure a massive negligence suit against Metro. The taxpayers are going to get hit as this is a "public" form of transportation. The engineer is wholly responsible for running the train and observing the signal lights. He allowed his attention to be distracted with a cell phone sending text messages. Modern locomotives are full of equipment to help the engineer do the job safely. They can't overcome negligence or stupidity.