as per the FAQ;
Q: Can Objective markers be placed on the upper floors of ruins
and similar terrain? (p121)
A: Yes, but not a fortification.
So on the landing pad fortification, no. Aegis could be a difficult matter; if it is placed in a continous line then technically you couldnt place any objective behind it as per the brb.
I would say the rulebook is pretty clear, they are both classified as fortifications, so the rule stands as written whether or not they are treated as area terrain or as purple monkeys, they are fortifications. Their type is fortification, they are purchased as fortifications, and they come under the heading of "fortifications" in the brb.
My take on it anyway!
“If an injury is to be done to an enemy, it should be so severe that his vengeance need not be feared”
- Archon Niccolò Machiavelli