Today I am suggesting the Washington Metro Red Line. It runs between Shady Grove and Glenmont. What makes this route unique is that the Red Line is the only line in the Washington Metro system that doesn’t share its tracks with another Metrorail line. It is the oldest and busiest line in the system. It forms a long, narrow U shape. The train that runs on it is: Alstom 6000 Series The service is operated by the Washington Metropolitan Area Transit Authority. Time period: 2032
If it has significant underground stations then unlikely as DTG have admitted to struggling with light baking in TSW. The other big if would be licensing or access for research, if the operator decided they don’t want their infrastructure and train systems replicated in a game for security reasons. And yes, OP, you would get your premise over much better using some punctuation and paragraphs (not wanting to be the grammar police here ).