And here's the bad, bad and bad news:
1. Import this very simple bird to Microstation (STEP format).
See any engine combo? No...because some translation havoc occurs and engines are some miles apart from the body.
Anyway some seconds later here's the corrected thing (with regard Geometry - but what about the structure of things? - by that I mean that the prop should be a void assembly of 3 wings that should belong to the engine that should belong to the engine assembly that should being instanced twice to the body ... blah blah blah).
2. Import the very same STEP file to Rhino. Hmm...still havoc but a different way of havoc.
At least some stuff is imported as "nested" blocks (but Rhino is NOT the app to start correcting things for MCAD usage - avoid at any cost).
3. Moment of truth : Open this STEP file into Creo.
Hmm...things are way better AND most importantly: the hierarchy of parts/3d objects (the way that this bird is "structured" in plain English) is retained.
This is quite evident using the Structure Browser.
Notice that Microstation fails completely to read properly Assembly/Component information...meaning that power is nothing without control, he he.
Moral: CAD is 1% data and 99% structure. With this in mind Microstation can't talk to any MCAD app the right way.
However there's ways to do it manually (but only if the structures are very simple).