I'm not sure what you want to achieve, but one possible solution is to save a GE image at the highest resolution (File -> Save then use the Map Options to turn off all except Scale; Resolution Maximum) and import that into SU as an image. You can then use the Scale on the image to scale image properly.
You can then place your model in SU, covering the GE image of your buildings.
If you want this to include terrain/ elevation, it's doable but more complex. See my earlier post for some of the details.