first off you can purchase 3d models of cities in different formats it just depends on what you are looking for in that city. look on the market place here or on 3dcommune.com, daz3d.com or even turbosquid.com

I don't think you can use the files from MS flight sim in bryce as the format isn't one bryce can use.I'm sure if you look in the free stuff on here or 3dcommune you could find models of river boats. I know they had one for sale at daz3d a while back but not sure now. 

I have opinions of my own -- strong opinions -- but I don't always agree with them.