Well, aside from only some of the track existing, there's no way in hell they would use heavy rail for more than just a confined line from St. George to Arlington. 440 is absolute garbage for passenger rail of any kind, the freight alignment is even worse (misses everything between Arlington and West Shore Plaza while cutting through industrial/restricted space), and the Arlington terminus would be a PITA to reach without being on top of it. BRT would be able to bridge the gap and serve West Shore Plaza without missing quite as much, lacking potential, or costing a pretty penny. It could certainly allow for rail conversion at a later date, though HRT is pretty much out of the question -- especially without TOD to help offset the cost.)