In the Canting, there is a certain spot in between the bench and the wall. If you jump and point the camera up, or keep pressing the crouch button you will eventually phase through the building. And, if you're lucky, when you get out of a turret that is on top of a building, you can fall through the roof into a room. You can't get out of here, but you can shoot grenades or rockets at the walls and ceiling, and if you're lucky a nearby enemy will be hit by the blast. And if you're a hero, Saber Throw can get people as well.
Yoda can get into basically any building where there is a purple tarp and the box beneath it. For the one nearest the Northern Hero's command post (the one next to the ammo droid), hop on the box and jump backwards into the building. Basically there is an open spot on these sides of the building, and you have to fit Yoda through them. Yoda can enter the big tall grey ship in the middle of the map by going around to where there is a thumb-tack like protrusion in the ship. Directly below that, there is a ledge and a disk right above it. Maneuver Yoda to where he is between the disk and standing on the ledge. Look at the meeting of where the disk meets the ship, then jump once. Repeat as needed, until Yoda breaks through. Tango and Bob Sett can also do this.