From the help file "Copies a triangulation from one model to another. Neither selection masks, boundaries nor transformations can be applied." - so you cannot simply copy the triangulation.
1. Create a grid and drape it onto the triangulation. Copy the grid up 300mm and triagulate thae grid.
2. Draw the triangulation, export to native dgn, copy the graphics up 300mm, drop (twice or more times) to get lines for each triangle edge - convert to strings in MX and retriangulate. This process takes a couple of minutes. This is probably the quickest way.
Once you have both triangulations, you can display them both on a profile (co-linear profiles)