So I had perfect test to use CE on a real project a carriage which hung from a Monorail that wound through a facility with multiple angles and radius's. The carriage was approximately 7ft long and 4ft wide with a pair of trolleys set 4ft apart off the center running the lung way of the carriage. I figured i could convert the center line that was my monorail travel to a B-Spline curve lock it so it wouldn't be aloud to move and set the center of my 2 trolleys coincident to the rail. Then i could drag it all over the place and verify that it didn't hit any columns or other surrounding equipment without spending the hours normally required to do so. Sadly it didn't work.
When setting any coincident to a B-Spline Curve it seems to always grab one end of the curve and doesn't let me grab the curve itself.
Is there another way around this? I even tried using the tangent constraint and it also just grabs the end of the curve.
Perhaps if the issue is using a B-Spline curve is there another kind of line element "string" I'm not familiar with that would support this kind of usage? When i attempt to set something coincident to a generic line string it will only work within the constraints of one segment of the string.
Here's a link to a post showing how to animate a box car along a b-spline path. This may help with what you are trying to do. It also includes an example dgn.
You should be able to scrub through the animation with the Animation Preview tool to view check clearances.