The building code and fire code thing is not true. Building codes are actually very flexible. There are plenty of ways to build a building to look exactly like almost any old building and fully comply with all codes.
Look like old buildings? Sure. But actually be the same? No. Hell, the building I live in is less than 12 years old and the electric panel is no longer to code, the HVAC condensate line is no longer to code, the damn stairs are no longer to code, the freagin dryer vent is no longer to code. They were all to code when they were built.