"And just how, pray tell, would calling the singals on the radio have prevented these accidents?" Several ways. One is that, if Sanchez had felt a responsibility to call the signal at CP Topanga, he might have been paying attention to that, rather than his cell phone. Second, if Conductor Hillenbrand had been expecting the signal to be called and Sanchez didn't call it, he might have contacted Sanchez over the radio about it, or (as I've been told) he would even have been correct to pull the emergency brake in the coaches.

Third, if there had been a general atmosphere of rules compliance (supported by management and supervisors at Connex), the conditions that allowed Sanchez to text while running the train wouldn't have developed.

I believe OPRRMS, who as far as I can tell has very, very close affiliation with events at Codnnex, has said here previously that on Metrolink, engineers are required to call all signals, while conductors are required to confirm the call if the indication is less than clear.