While you may send what ever calling ID you wish for regular calls, the local LEC treats 911 calls very differently and typically puts them through 911 screening tables that only allow the CLID owned by the account to pass. If another number is there, it can be stripped out and replaced with the billing number. Entirely up to the carrier.
Regular Calling Line ID to your cell phone may be totally different that Calling Line ID (ANI) to the PSAP 911 center.
Testing to 911 can be established by contacting them on the NON EMERGENCY NUMBER, and requesting to speak to whomever is in charge of test requests. They will tell you the policy and guidelines for that agency. This was NOT designed for general public testing of the Text service, and you could easily overload the center when an event is happening.
Don't guess, play it safe, but remember, if too many people start to test before a policy is set up, you are going to have a negative impact on the workload of the center, and they will discontinue the service. Not good for anyone.
Cellular phones can use several technologies that can assist in providing and X,Y coordinate of the device. These can be extremely accurate, depending on the data available. Look on Wiki for 'SkyHook'. This information is NOT available to 911 on phone calls, nor dopes a data channel exist to even transmit the data from the device to the 911 center. This is why the App is useful, but the App, needs to talk to something on the 911 center side. Without that piece, there is no way to get the information from point A to point B.
This is based on a report by FindMe911.org and it is specifically talking about issues in the Washington DC area based on data obtained from a FOIA (Freedom of Information Act) filing by that group. It is not to mean that this is the condition all over, while I will admit there is a problem with cellular phone location as the GPS signal is seriously disrupted inside of buildings due to the lack of Line of Site.
Yes, this is a problem, but this 90% error rate is based on statistical data from a particular area.
Regular Calling Line ID to your cell phone may be totally different that Calling Line ID (ANI) to the PSAP 911 center.