Here's probably more than you ever wanted to know about this....
It was offered on my westbound Empire Builder on December 27. The train was sold out and us coach pax were warned that we may not get a dinner reservation (indeed this was the case...the waiting list was started long before the diner clerk reached us). Mrs. fairviewroad and I had not been planning to eat in the diner anyhow, having brought some food with us. But, we decided the purchase one chicken dinner to split between us.
It cost $9.75 though oddly the cafe attendant said the price "used to be $11." $11 would certainly have been steep....$9.75 was on the upper edge of reasonable. The plate included two largish piece of chicken as described by the previous poster. It also included a small dinner roll, a small fruit salad, and a small cobbler-esque dessert. All were acceptable. The cafe attendant said he'd thrown in a bottle of water (again, it was a "small" bottle) as well as a coffee. So, for $9.75 we got a nice splittable meal that was certainly better than the cafe car food and probably on par with the diner chicken in terms of taste if not quantity.
The announcement was made mid-afternoon. The cafe attendant asked people to pre-pay, and put my name on a list. He ordered a few extra for crew and people who later changed their mind. Since the train was running about 75 minutes late (not bad, actually...and we arrived only 15 late into PDX) the Havre stop came right around 5 p.m. (right after the friendly border patrol goons made sure the train was free of terrorists, but I digress). The cafe attendant announced about 15 minutes after Havre that those who ordered could come down and pick up our meal. The chicken was cold, and some people preferred it that way. But the attendant "nuked" the entree portion on a separate plate for those, like me, who wanted it warmed up. Additionally, the attendant--prior to serving the chicken dinners--went upstairs in the lounge car and chased people away from about 4 tables so that those of us who ordered the chicken dinner would have a place to eat. So it became a diner-like "shared meal" experience. The people he chased away were a little put out but these were people who had been camped out there all day playing video games, etc. So I felt no pity.
It is my understanding that the business in Havre that supplies the chicken dinners also supplies the cold breakfast plates for the PDX-leg sleepers. The cafe attendant also said he ordered 40 ham/cheese sandwiches from the same company because he knew he'd run out of food otherwise. The chicken dinners sold out but the ham/cheese sandwiches were being offered for breakfast the next morning. No thanks.
All in all this was a good experience. Not a fine dining experience but a very nice, very thoughtful planning on the part of Amtrak. I don't know if they make money on this or whether they act as a pass-through for the Havre business, but either way it's a nice mini-economic boost for either Amtrak or the Havre company.