Honestly, there are about five or so pages worth of rules missing from the 40K rulebook. Actual rules, rather than a haphazard mixture of about three sentences of actual rules, several FAQ questions, ancient precedent, and assumption, to cover this situation isn't actually present.
The closest the rules come to covering the situation is one the FAQ answer stating that area effect psychic powers are measured from the vehicle's hull, so presumably one can measure to the hull for the psyker model in that situation. For psychic shooting attacks, the range and line of sight for shooting attacks use the fire point rather than the model, so by extension one would measure from the librarian to the fire point.
I was actually inquiring about the situation of having a model with a Psychic Hood on the table, and trying to deny a psychic power used by an enemy from inside a transport.
Lets say there is a Chaos Sorcerer inside a Rhino, and a SM Librarian who is on foot.
The Chaos Sorcerer uses Lash of Submission on the Librarian from the fire point on the Rhino.
Will the Librarian get a chance to negate the psychic power?
Give reasoning behind the answer too, and not just a "yes" or "no".
EDIT: Sharrington, read the rule again...
"Declare the you'll use the psychic hood after an enemy model within 24" of the librarian passes a psychic test.
Technically, there is no model.