Yes, you don't (in most countries) need a SIM for 112/911, and even when you do have one, you are allowed to use other carriers for such calls, even when you ordinarily shouldn't be able to roam onto them.

The specs do have that, but I used to work at a major mobile telco which didn't implement that part of the spec. The argument was that people would use emergency calls to test phones without a SIM. That may well have changed, but you can't assume that the spec will always be implemented in the network.

Interesting, in the US this is a regulatory requirement and the decision is not up to the telco.