Question:

Can I use entity snaps with my existing 3D entities, to accurately draw new 2D linework?

Answer:

Yes, absolutely!  embeddedCAD, inCAD and MicroSurvey CAD have a 2D/3D toggle setting that has the following effects when enabled:

1. All point nodes are redrawn at zero elevation.  The correct elevation will be retained in the database so that you can redraw them at elevation later.
2. A setting _OSNAPZ is set to ON.  This allows you to snap to enities with elevations and the X,Y coordinate while be honoured while the elevation will always be set to zero

Find the 2D/3D toggle in MSTools | System Toggles | CAD Drawing Controls and turn on "2D Point Nodes"

TIP: If you prefer the default vertical datum to be something other than zero, type ELEVATION and enter the desired elevation.