[Fair warning: I've yet to play any Luke Crane RPGs; I've only read Burning Wheel and some of Mouse Guard, so what I have to say is highly speculative.]
For those of you not familiar with the comic book Mouse Guard, I highly recommend it for the aesthetic appeal alone. It's sentient, bipedal mice in a world without humans; they wear little cloaks and have weapons and castles and the like, and the titular organization's goal is to mind the roadways of their little world, thwarting predators and the like.
Sadly, as beautiful and clever as it is, I've yet to be engaged very much by the storyline. The conflicts the characters face are gorgeous and lush, yet somehow hollow and a tad forced. The lovingly rendered yet ex-nihilo legend of "Black Axe" (a traitorous villain with a titular weapon) seems tacked on, although David Petersen, the creator, spins the tale with all his artistic talents operating at full capacity.
This all being said, I was wondering if the RPG translation of the series would have potential for greater storytelling powers, but thus far I don't know what to think. In the RPG text itself, the designer (Luke Crane) puts it right out there as far as the point of play: the game-master throws challenges and obstacles at the players, and they play their Mouse Patrol the best they can to overcome them. That's a straight-up, definitive example of Gamism, right there.
I have never played an explicitly Gamist RPG; I've played a few games that were highly Sim, with lots of Gamist tactical content thrown in, but never anything that went right out and said, "This game is about winning and losing. The rules are here to determine when and how that happens." Kudos to Mr. Crane for clear Creative Agenda in his design this time around. I was inclined to agree with Ron Edwards about Burning Wheel, and without putting too many words in Edwards' mouth, the agreement runs toward the analysis of BW being "motorboat" Narrativism: design that almost nails Addressing Premise, but falls just short and instead roves off into highly Simulationist, High Concept play.
If you don't believe me, compare the section on Beliefs and Artha (make-yer-own-Premise Narrativism, which is unique, I believe) with the Lifepaths section of the Character Burner (such theme and panache in those different Race Chapters!). Artha and Beliefs encourage a sort of internal regulator for the character and the decisions the player makes, but as to what sort of story all this is for, Crane has left it up to play groups to determine. In the Character Burner, there's no question that he can beautifully portray something akin to a whole barrel of story seeds, even if the attached mechanics are based on "realism" more than player agency (in terms of helping to tell the story, not in terms of raw power).
My point? Well, I feel like this is Crane's take on almost-Nar-but-really-Gamism. That claim is quite a stretch, I admit, but here's one little tidbit from an RPG.net review that gave this idea a germ of life:
"The Nature rules deserve some special mention. All creatures in MG have a Nature specific to their species. Mouse Nature is used for Escaping, Climbing, Hiding, and Foraging. Nature can be called upon for these basic activities, but it can also be substituted for any other skill. Doing this, 'going against your Nature,' risks taxing your Nature, and there are risks to reducing it by too much, or for that matter, for raising it too high through advancement."
Does that not seem like a two-steps-removed crack at Premise to anyone else? It seems as though there is a line for PCs to walk with regard to acting "properly Mouse-like", but if I recall, this was something that wasn't really established in the comic. At least, not in Series 1: Fall 1152. This bit makes me think, "Mouse Nature... as opposed to what?" It's intriguing, and it makes me want to go back to the bookstore and find out the rest of that mechanic, to see what Crane is on about.