Dude dont answer questions unless you have quotes because chances are if your just telling how you think it is then your wrong just like now.
A unit can embark onto a vehicle by moving each
model to within 2" of its access points in the
Movement phase. The whole unit must be able to
embark – if some models are out of range, the unit
must stay outside. When the unit embarks, it is
removed from the table and placed aside, making a
note or otherwise marking that the unit is being
transported (we find that placing one of the unit’s
models on top of the transport works well!). If the
players need to measure a range involving the
embarked unit (except for its shooting), this range is
measured to or from the vehicle’s hull.
• If the vehicle moved before its passengers got
aboard, it may not move any further (including
pivoting on the spot).
• If the vehicle has not moved before its passengers
got aboard, it can move as normal.
All abilities that measure how far you are from a model are measured from any point on the hull when your embarked on a vehichle.
So before the recent GK FAQ, ive been expecting you was measured from the hull of the tank. You needed fire points to shoot out of and a fire point to measure line of sight to coteaz but it worked.
Unfortunately the Rulebook FAQ said...
Q: Can models embarked upon a vehicle use its fire
points to draw line of sight to a unit to use special
rules or wargear (other than shooting)? (p66)
This means that Ive been expecing you is still measured from the hull but the firepoints cannot be used to draw line of sight so you cannot use the ability.
If it was an open topped transport i think it would be a different story but GKs cant get one.
So short answer is yes but you cant do it any more.