The Northwest suburbs (Boulder, Louisville, Lafayette, Broomfield, Longmont) got quite screwed over in this deal - we approved and paid into the 0.4% sales tax in 2004, but ended up with only years of disruptive highway construction leading to a privatized tollway and fake Bus Rapid Transit. We didn't even get real BRT as the buses run in the private toll lanes rather than their own grade and the buses board and debo…
36 is starting to show a lot of progress for the dedicated bus lanes and the train tracks which will eventually go to Longmont. It was always the plan that the south and airport would go first. The north is scheduled to be done in 2017 I believe.
There's going to be light rail to South Westminster (South of 72nd), but the train tracks to Longmont are only being "researched," aren't part of this phase of construction, and are one of the reasons RTD are trying to pass an additional 0.4% sales tax.
The original concept was that the Northwest Rail project would proceed along with the other rail projects - to the point that housing developments like Steel Yards were built next to Boulder Junction in anticipation of the "coming train station." The original project plan involved running RTD and BNSF freight trains on the same shared, standard-width, diesel-powered rail line, not unlike Caltrain in the Bay. You can see that map here: http://www.rtd-fastracks.com/media/uploads/nw/2009-0715_NWR_... (stations in Red were purportedly "funded" by the 2004 tax).
That plan was scrapped for a variety of reasons: RTD couldn't come to an agreement with BNSF, they would have had to use eminent domain and pay a lot to build a rail yard, and they straight up mismanaged and ran out of money.
The new plan is that there's no plan: RTD are conducting a "Northwest Area Mobility Study" and even if an additional tax were to pass, it's unlikely we'd see a working rail line until the mid-2020s at the earliest: http://www.rtd-fastracks.com/nw_1