The GIS industry has the OGC. What standards does CAD software have?
It is surely the Open Design Alliance (ODA). Their product is called Teigha:
Designed by the ODA, Teigha® is available on all major operating systems. It supports the use of C++, .NET, and ActiveX interfaces and allows the exchange of data through .dwg, .dgn, .stl and .pdf files.
(Early on it was called OpenDWG but some private company got all lawyerly and put a stop to that.)
They are industry driven and dictated by your customers requirements, and deliverable requirements should be outlined in a contract. I am sure your state DOT has a CAD/microstation specification on their website available to the public (assuming your in the states). If you are in the UK there is the AEC https://aecuk.wordpress.com/
Basically the answer is there is not one and it varies with organizations and industries.