Unless you explicitly enable Advanced Protection mode for all your devices, Apple stores your key in their servers and will give it to whoever legitimate looking asks for it. Aka ICE etc will definitely be granted access.
If you decide that everyone is lying to you all the time, you can't build a useful model of objective reality. You just end up frustrated and not taking simple actions you can to make improvements for yourself and others. Don't fall into that trap.
I don't assume just know history, PRISM. I don't see how not trusting apple means I can't trust anybody. On hackernews people should know better to trust anything but transparency (source code) which might as well be the dictionary defined opposite of apple.
This is very easy though, you just go to your iCloud account settings under the settings app and enable it. It should be on by default imo, but I understand the argument for why it isn't.
Either way, enabling it is not a barrier and ICE cannot be granted access once you do unless you yourself give them that access.