In my I'm not a lawyer, reading of the law. If a phone has the ability to dial, it should be able to dial 911. If you pickup a phone and there is no dial tone it would be almost the same as not having a phone at all. The same would go for a phone with no dial pad you wouldn't assume that it would be able to dial 911.

Our first option that we presented to them that they immediately discounted was to have the phones set to off hook dial an attendant station where the call could be dealt with no matter what it was.

The Cloud is just someone else's computer!