*Apparently* emergency services have a way to over ride your code, but I dunno how true that is. Interesting question and I've wondered the same thing. Only recently I put a code on mine to stop my kids prank people and playing games!
No, they don't have magic ways of hacking phones. They are just regular people! Imagine if all the emergency services personnel knew how to break into every phone or tablet out there. There'd be an outcry.

How come more people don't know about that emergency call thing on the samsung? I didn't know. That's cool.