In the Burning Wheel family of games, there are various principles that govern "say 'yes'". Burning Wheel uses the DitV approach - say "yes" if nothing is at stake (where stakes are defined by reference to PCs' beliefs, instincts, traits, relationships, etc). Torchbearer uses the "Good Idea" approach - if the players come up with a good idea, the GM unfolds the situation from there to frame the next obstacle. I don't know how Mouse Guard does it, but I'm pretty sure it will have a discussion of it somewhere.
Interestingly, you won't find this in Mouse Guard. The way Mouse Guard (the book) is structured isn't the typical "GM Section" and "Player Section." Its structured as procedures which address either relevant party as it moves throughout (with a particular mouse icon for GM instruction and another for player instruction). Whereas you'll find "The Good Idea" in the GMing section of TB (Tricks of the Trade), you won't find such in Mouse Guard’s Obstacles or Missions or Conflicts or even Sample Missions sections. There is a reason for this I'd say. While all 3 games are in the same family and share a massive swath of engine and architecture, they also have some key diverging features. In my reading and running of the game, my interpretation of Mouse Guard is that it is intended much more as an MHRP Action Scene/Transition Scene aesthetic or Blades in the Dark Score + Downtime than either BW or TB. Its obviously closer to TB than BW (with TB basically beng a reskinned MG with several other layers added in and an outright genre/aesthetic/trope change), but there are some key differences in several areas between even those two. If you recall, I start my TB games with players having 1 Persona and Fate...that is from MG. You get 1 Free Test in Player's Turn (Camp and Town equivalent) even with no Checks in MG. Player's Turn can break up GM's Turn (Mission or Adventure phase in TB) in a much more hospitable and fiction first/freeform way than the procedure-intensive and gamestate-integrity-dependent Camp phase does in TB; you don't have all of the peril and intensive procedures to get to Camp phase and its an outgrowth of the fiction or the meta (are we at a safe haven or a break of the Mission phase where it would make sense, meta or story, to have a Player's Turn?). Beyond that, you don't have the crushing Grind, the crushing demand of Inventory/Gear/Light/Food & Water, Circles plays a role in the Wilderness, and there is no delving (this is a game of Ranger-Knights performing the duties of the Territorries to keep it safe and harmonious and it’s infrastructural integrity upkept). There are plenty of other differences in nuance (and a host of "oh Torchbearer/Mouse Guard come from the same stock" as well...obviously!).
When its GM's Turn (Score or Action Scene equivalent), you could look at play something like a Complexity 1, 4e Skill Challenge with 4 Obstacles minimum (assuming all successes) but also Complex Obstacles (nested SCs in 4e or Linked Tests in BW) here and there (eg when you need to harvest stuff to make a boat > craft it > pilot it) and, of course, Twists as they arise (which could be seen as Failures in the Skill Challenge; and yes, they of course still have “Fun Once” for Twist handling).
So on the whole, I would say (a) MG’s feel is much more Closed Scene Resolution like MHRP or 4e (but MHRP specifically because there is no A Good Idea to overcome Obstacles whereas you have the equivalent in 4e) and (b) it is a much less intensive game than either BW or TB (in all the ways those games converge to be intensive).
Now intensive doesn’t mean intense. MG is very fast-paced and intense. I love it (it’s right up my alley in virtually every way). And the dangers of Natural Order means that death and memorializing your heroic member of the Guard feels and
is on the table waaaaay more than it is for your standard D&D game.
I’d run it more, but it seems like some folks aren’t keen on playing heroic mice in a fantasy world below our human feet.