Conditional line up after a landing aircraft - you can cross the holding point as soon as the lander has past you.
Conditional line up after another departure - you can cross the holding point as soon as there is sufficient space.
In either case, pilots are expected to exercise their own judgement wrt to jet blast or prop/rotor wash. (as you would when following another aircraft on the taxiway).
Stick strictly to correct phraseology, as already mentioned.
If the red stop bar is still illuminated, or any other doubt - query it before moving.