I don't know the circumstances of those two, but I'd suspect they've suffered lasting wing injuries along the highway and have been rehabbed but cannot be released into the wild.
Unfortunately, the highway is the graveyard for many eagles, which are attracted to the never-ending carrion supply from kangaroo and emu roadkill. With their massive wingspan, eagles can't quickly fly off when a vehicle approaches and even if they aren't killed on impact, the blast of wind (especially from the huge trucks), will often knock them out of the air, leaving them broken and bleeding by the roadside, to die a slow death in the heat and dust.