Offhand, I think you will have to clone the polyline, then use vlax-curve functions to locate the points in the current drawing and then delete the cloned polyline unless you want to keep it. I am not experienced with the CopyObjects method, so I would use nentsel and create the clone using the transformation matrix and entmake. That is what I do in my XOFFSET command function mentioned here recently in another thread.
I just don't know if the vlax-curve functions will work on a nested object, at least probably not without transformation. Then again, if the xref is inserted at its basepoint, and scaled at 1.0, and not rotated, and the polyline is not nested in another block, or its block is at the xref basepoint and not scaled and not rotated, then you can probably avoid the transformation.
If that's the way you want to go, then I could extract my code and post it. As I remember it was a lot of work and I would have gotten nowhere without the help of Joe Burke (of StripMtext fame with Steve Doman) and the other usual suspects of days past.
