I made a rather deep analysis of UlanBataar, a few years ago. My conclusion was :
PC12 for domestic flights
ERJ145XR for foreign flights.
And that's it. There is no other choice, and you're bored to death once you filled 12 planes or so. And Cargo is a no-go either.
Of course, neither PC12 nor ERJ145XR are available in 1955,which makes the country basically unplayable.