And for a mechanical contractor to draw everything in 3D is getting more and more common. I worked for the mechanical contracting business for 6 years as a CAD Designer and I used AutoCAD MEP because I got much faster than plain vanilla 2D CAD, not to mention I could coordinate my own designs for the field. It makes so much sense to do that as a contractor so you are "error free". I remember a big chilled water datacenter I designed. It was an aggressive schedule, almost completely unrealistic but because I was very proficient in AutoCAD MEP and I knew the field very well (worked in the field from 18yrs - 21yrs old) I was able to provide cut sheets to the pipe supply company to get pre-cut 16" carbon steel pipe for a double redundancy job. This took LOADS of time off our guys measuring and field cutting with a hand torch, since I designed everything in 3D. 16" diameter pipe all the way down to 3", mostly all pre-fabbed using AutoCAD MEP. Granted a lot of responsibility relied on me and I did goof a few times but the bigger picture is I used real-world 3D environment to take all the time/labor/errors out of the job.
Not trying to toot my own horn, but merely giving an example of how a complete 3D model from a mechanical contractor can have other great benefits from my own experiences.