I agree with the VOR separation that some places use 15NM for outb/outb, and 20NM for outb/inb or inb/inb.
The reason for this thread is actually provision b) where a departure takes-off using the duty runway and makes a turn which keeps him outside of the 45° of the reciprocal track of the arrival (see figure 5.38 in Doc 4444). Can the departure clearance be an altitude above the inbound if the clearance is only valid until 3 minutes before the inbound estimates to be over the threshold. Or does this paragraph only clear the departure aircraft below the inbound aircraft and when airbourne to come up with separation to allow the climb/descend through.