I've used pro in architectural concept designs... but never for final engineering drawings - Pro's too good for that .
Back when I was running my own business, I picked up a cheapy 3D home design package from Wal-Mart here in the states, that was written by Broderbund. It had all the codes already implemented into the software, so all you had to do was place where you wanted lights, switches, plugs, and then the software would automatically run the wiring for you, and correct any misplaced items that were'nt per code.
I think I spent about $40 (U.S.) on it. It even had rendering capability!!!