I have connected in Denver hundreds of time and taken the train from concourse B to bag claim as well, which invariable stops at concourse A. The widebody from ORD will arrive at a gate very close to the tram, most likely B32, 36, 42, or 39. This means that from when the door opens on the 767 to when you get to the tram entrance should take about 3 minutes if there is no dealy getting on the train. The train itself will take one minute, with a wait of up to three minutes. Thus, I'd give yourself 10 minutes from the airplane door opening to getting to the CO gate. This assumes you dont stop anywhere but you should be fine if the flight arrives reasonably on time.