Red Alert 2 introduced building garrisoning, is this a feature in Generals?
Oh yes. A much improved feature at that. The new SAGE engine allows you to garrison any unit in buildings and even combos of units. The engine also allows for situations in which you can drop forces on the roof tops of garrisoned buildings and have your troops try and take over the building. Imagine a helicopter hovering over a building and then special forces infantry are roping down from it onto the building and starting to dispatch garrisoned enemies. In addition you can put anyone inside. With the new command bar style you can click on a building to deploy who you want rather than having them all pop out. This also means you can have anti-air, anti-infantry, anti-tank combos which make them even more strategic.