Sorry to keep bringing up USRail21's posts.
I think this was a part of the plan envisioned by Governor Bill Richardson of New Mexico and the Governor of Colorado at the time the New Mexico Railrunner was envisioned. Since NM had to buy all the track up to Trinidad anyway, it was thought that the NM Railrunner could go all the way up to Denver. In the other direction, the dream was to connect to El Paso. Denver to El Paso - Maybe even add Boulder and Fort Collins in the North.
But alas, at nearly 12 hours of run time, it would be an extraoridary long "commuter" train - and only servicing 3 major population centers.
It could also potentially have the effect of putting in an express lane for drug trafficing from Mexico, but hearing how DEA has been riding the rails, this is unlikely.
So what happed to the Good Governor's dream? Colorado bailed, and the costs ran out of hand. No one figured there would be a payoff for this route. Though, quite frankly, in a rail environment where the flow moved from the West to Chicago, any connection - whether it be a NM-CO Snow Runner or Amtrak - would be welcome.