sorry for so many posts..I will add there are so many different types of plans for buildings too mate...some are as follows

structural : all things to do with the concrete/steel/components used
architectural : as above but usually contain the fittings and artistic section
electrical : conduits etc
plumbing : speaks for itself
floor plans : the layout of the floors (interior) and dimensions of the building
building elevations : the exterior dimensions and 'look' of the external refs

there are many more but this will give you and idea I hope...or confuse the hell out of you LOL

cheers bullet

EDIT: Nilla is right...if you want accuracy you would need to use ACAD first then import the DWG into Maya...I have dabbled with this a bit with terrain modelling etc and for the layout of roads...its not hard but sometimes Maya doesnt open them well. I am doing my bosses house on the side as a test project...sadly a lot of designers when they give you the plans purposly leave out dimensions...so you cant use the plans..LOL sneaky