The key word here, folks is scope. If there is a civil suit as regards to texting on Metrolink over a period of time, anything conceivably within that time frame is open to having a judge authorize a search warrant for it's record. If it's investigatory as to the cause of the crash, the window is going to be considerably smaller in scope, and therefore less of a time span would be allowed.
As regards to information regarding backgrounds, etc., which are often reported, understand that we are talking about court orders here for documents (search warrants). There are many ways to get information as well, ie. from witnesses, evidence, etc., often without the need for a court order. As regards to official documents, almost all of the time in such a matter, a court order is requested so as to make the evidence stronger in a court of law should there be a dispute as regards to the suitability of it's introduction.
And, no - with the exception of the Patriot Act, the Federal government has no more law enforcement powers than does store security at Walgreens with "Special Police" powers (within their respective jurisdictions). Constitutionally, the law applies to all law enforcement equally.
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Paul Joyce passed away in August, 2013. We honor his memory and his devotion at railroad.net.