Not sure what objectives means. Its not like you have to build on them to win the mission or something.
Think of Company of Heroes/Dawn of War resource points - fixed sites you capture to obtain ammo/energy/manpower and can build on to increase the output of this resource, or Shogun 2's multiplayer map buildings (capture to obtain effects such as increased ammo for archers, increased morale etc.)
As far as actually building this kind of 'objective building', that too is showcased in games like CoH (medic facilities that heal troops, for example, or the German veterancy buildings that improve soldiers' level), or Wargame: European Escalation (fuel depots and repaor facilities).
And most RTSes, both modern and traditional, include buildings that unlock upgrades for certain units, which amounts to much the same thing - Academies in Cossacks, Engineering Bays and equivalents in Starcraft and many other games' counterparts only act to unlock these kinds of upgrades, be it +1 attack or amour for infantry units, speed boosts for a specific unit type such as Banelings or Zealots, siege mode for siege tanks, or new psionic powers/equivalents for High Templars or Infestors.
In the new Starcraft expansion (in the latest incarnation of the beta), you don't even need to pay for an upgrade to use the Armory as an 'upgrade building' - build one, and you automatically get the Hellbat ability for your Hellions. For more esoteric benefits, a Zerg Creep Tumour (Starcraft/Starcraft II) is a structure which generates terrain that benefits your units.
I think the AC reference refers to the terraforming of tiles - this worked basically like building improvements on a tile in Civ games, but with more options.