When will the regular Denver station be reopened?
The official word is "2014", but they've never said *when* in 2014. It's not clear when.
There's several separate projects going on.
The bus box is built and the bus terminal is getting final finishes. The trainshed and canopies are mostly up. The platforms are partly poured. So the trackside stuff will probably be done on time, or early. Unofficial information from 2011 said that the bus terminal was expected to open in April 2014, Of course that's old information... and the bus terminal could easily open before the station proper does, since it has an entrance from the other end.
The main station building is also being altered and rearranged for the hotel, under a separate contract (sigh). That project started later and I haven't heard *any* word as to how fast that work is going. That includes Amtrak's operational space, so at least part of it has to be done before Amtrak moves back in. That's why I won't be surprised if Amtrak's return to Union Station slips into early 2015; it depends on this project and I haven't heard any updates on it.
There's yet another project rebuilding the open space in front of the station (formerly parking), two office building projects adjacent to the station building, and a third adjacent to the platforms.
Then it won't be until 2016 that the commuter rail actually starts running out of the station.
The station platforms for the rebuilt Union Station have an interesting design. All the passenger platforms are at the same level, but not all the tracks are at the same level. The commuter rail has top-of-rail 48" below platform height (providing level boarding). I believe the Amtrak tracks have top-of-rail 18" or perhaps 15" below platform height (providing level boarding). There are two Amtrak tracks with side platforms; there's also a narrow service platform between the two tracks for Amtrak to service the trains, which I presume is lower. There are two tracks because the track layout was designed when Ski Train was still running. Anyway, it will provide Amtrak with substantial flexibility for delayed trains, special services, etc., especially since the "temporary" station platform and track will be retained and can be used for cut-off cars, protect engines, etc.