All you really have to do besides laying a few mines inside the building is have two players purchase either a Light Tank/Mobile Rocket launcer (GDI) or the Stealth Tank/Light Tank for (NOD)and one engineer for repairing.
Have them place themselves by the entrances of the building at an angle ( so your free to fire at the incoming APCs/helos/you name it.......once they see that your blocking the way they get thrown off and rush whatever building is near them which usually results in death because the AGT/Obelisk nails their ace!
It works good because their armored enough to take a few C4 hits from the rushing engineers and by the time they reload they should be dead (depending on the skill of your teammates).........
This works particularly good against the rush of Stealth soldiers, all you have to do is rock the tank back and forth infront of the power Plant entrance and when they try to get past they get the good'ol "squish!"......
I've won more games this way when you have a team that understands what your trying to do and its usually the engineers that volunter because they spend most of their time in the base anyways........