Update: I never received an answer from the FCC. I contacted 5 persons without success. Nobody understand the scenario and they all need to send me to someone who's "technical", but then it'd dead air. I give up.
My point is simply in the USA which is a country of law suits, if a end user had to make a phone call where they have no cell phone reception but only WLAN to 3CX, and the 911 call never reached the PSAP, then there could be major law suit against the employer first, then employer to 3CX installer if they have one, then installer back to 3CX offices in Florida. Just my 2 cents for North America.