For a couple of miles immediately south of downtown Miami, the former FEC has been gone for a long time. There was service to Homestead into the 1980s; when I was working in Miami in 1981 I used to see the local along Brickell Ave., right next to where they were erecting the supports for Miami Metrorail.
South of Government Center station, Metrorail is on the old FEC ROW across the Miami River and then south. The FEC reached its Homestead line from Hialeah via a belt line that ran south past Miami Airport to a junction somewhere along Brickell south of the river -- don't know exactly how far. For a brief period, the FEC and Metrorail co-existed before FEC abandoned the Homestead Branch.
Randy Resor, aka "NellieBly" passed away on November 1, 2013. We honor his memory and his devotion to railroading at railroad.net.