This is tutorial I created to show a good workflow I've worked out in AfterEffects (CS5.5) using The Foundry's 3D Camera Tracker to match-move any 2D object (like a sign) that needs to stick to a surface within footage that was filmed with camera perspective changes (i.e. non-nodal). Because of the perspective, trying to 'stick' items onto surfaces can be a pain depending on the order you do things. If you find yourself constantly re-orienting and re-positioning, DON'T. Just watch and learn!
1. A simple workflow that solves the common problems of your object not "sticking" to your surfaces (key sequence: Parent, Turn on 3D, Adjust)
2. Creating garbage matte to hide foreground buildings where needed for your sign/object to pass behind
3. Hiding the building's original sign by creating a "hole" using a camera-tracker created shape to create an alpha inverted matte, rather than animating a subtract mask yourself.
FOOTAGE LINK: Here's the website link I promised - the 8 dollar DVD of "discontinued" NYC aerial flyover footage. Fifteen 1080i videos, including the one I used. It's a good deal, considering it used to be 250 bucks. And even THAT's cheap for stock video.