Thank you, Sigoroth, for the answer - very good of you, sir.
Mycen, indeed - referring to my copy of the Armada book unshielded vessels are said to take an automatic hit. Upon reading the 2010FAQ (page 29), I took it to mean that instead of the 'automatic hit', a ship would only take damage if a 6 should surface - much in the same way as blast markers.
I can only speculate, but I imagine this alteration may have been made to remove the 'instant death' for eldar escorts and the like if they happen to cross a tyranid's path.
I would also suppose that the effect manifests itself irrespective of who is moving.
Thoughts?
Thank you kindly,
LDTM