How about explaining how a TRE passenger on a TRE train on TRE tracks involved in an accident NOT involving AMTRAK can sue AMTRAK ... that just does not compute.
The worrisome situation is where a TRE train, run by a negligent TRE engineer (who is perhaps speeding and ignoring signals), smashes into an Amtrak train. Perhaps the Amtrak engineer cleverly manages to handle his train to avoid injury to Amtrak passengers. The TRE passengers sue Amtrak because... well, because they can't get any money from TRE, due to the Texas liability cap, so they're fishing around for someone to sue. Why on God's green Earth should Amtrak have to deal with that?