I'm designing a map and I'd like to make it so I tank could push down a garage door. I know the tree models can do it, but I don't know if it's possible to do it with just a brush.

I'm thinking a trigger here, but then anything would "trigger" the trigger. Could you be creative in the placement of the trigger? Have to blow the dust off my mental cobwebs, but isn't there a vehicle toggle for triggers?

Then build a breakable wall a-la the church tower in Foy.

Not quite what you're looking for though.

Maybe exploders are what you want.

Check out this link
http://www.modsonline.com/Tutorials-read-239.html

either exploders or a scripted event using a trigger multiple