Most as-builts that utilize point scan clouds are already modeled; the scan is to verify construction variances. So a BIM would have been created to get the permits and construciton documents, then a scan would be overlaid to confirm the final results and make adjustments for construction changes.
Scan Cloud registration software (Recap & Cyclone) can generate planes/surfaces and basic shapes from the scan cloud to allow modeling from the point cloud, but this generally results in a very large file size and is often not very accurate (the walls will not be plumb, for example). This works fine for simulations and gaming, though.
Good luck!
