Bookworm - the criteria that you have quoted relate to multiple line up clearances - ie have more than one aircraft lined up at any one time and NOT to a conditional line up clearance. EG - c/s via A1 line up and wait rwy xx, number 2 for dep to the type lining up ahead of you" - therefore you can line up now. Which is why you won't get that clearance at night ( or if any of the other conditions are not met)
Conditional clearance - " c/s - after the departing/ landing type via A1 line up and wait rwy xx" - therefore the departing /landing aircraft will be passing you and then you can line up. The only condition there is that the controller can see both aircraft, and the it is reasonable that the aircraft given the conditional clearance to would see the aircraft that the conditional clearance relates to. ( ie you at the holding point can see the dep/landing aircraft)
I think I've explained that properly - but then it all makes sense to me!!!!
louby