Perhaps someone will help the following:
If you connect AcePageManMgd.dll (standard path C:\Program Files\Autodesk\AutoCADхххх\Acade\) to the project in the Visual Studio environment, you can include Autodesk.Electrical.Project namespace.
This will give you access to the AutoCAD Electrical project properties, among which, in this case, the following method will be useful:
Dim acActiveProject as Project = Autodesk.Electrical.Project.ProjectManager.GetInstance().GetActiveProject()
Dim strDbPath = acActiveProject.GetDbFullPath()
