Lethal force is only authorized for the civilian bystander to prevent a rape or a murder. Not property damage. This assumes that whoever's attacking my property has a big sign on his forehead that says I'm here just to damage property and I definitely won't hurt any people.
The reason that we acquit someone who kills a home intruder is we assume the robber was prepared to kill the homeowner if needed. One contemporary rabbi actually was home at a time when most people wouldn't be, and found someone breaking in (who beat a hasty retreat). This robber was not prepared to use violence (he figured it would be an empty house), so the rabbi was not authorized to use any force (not that he likely would have anyhow).
Per Alex's answer on the above question, if your animal is attacked by another animal in a neutral space (or it invades your yard), if the only way to save your animal is to damage the attacking one, you aren't held liable. Thus I'd presume property is property. Of course we could have the funny case of a million-dollar throroughbred attacking my, Idunno, sixty-cent goldfish, and some evil genius has constructed a machine whereby if I don't push the button, it kills my goldfish; if I do push the button, it kills the horse; and those are my only two options -- save myself sixty cents, or cost the other guy a million dollars. As far as I know, strictly speaking if you pushed the button we can't charge you -- people panic when their property is threatened -- but I'd strongly assume meta-halacha would recommend that you don't.
