Since I wrote the software for a 911 CAD (computer aided dispatch) used by a primary PSAP (public safety access point) -- yes.
But... The 911 operator has to initiate the SMS exchange. Kind of strange. I believe that, in certain jurisdictions, TDD service for the deaf was a revenue stream for the incumbent telcom carrier. So, cell phones are specified to have to be "registered" to allow 911 SMS (this is just my speculation). The 911 operator has to initiate the exchange (in the areas that the system I work on is used).
Incoming 911 data already contains location data (from tower triangulation, etc.). More interesting is that the 911 operator must manually request location updates (secondary reports) and that these cannot be requested more frequently than 35 seconds apart (again, these regulations apply in my area). Again, stinking regulations.
Anyway, the data available (formats) are documented by NENA (National Emergency Number Association). www.nena.org. But... carriers (Bell, Telus here) use supersets of those formats.
The problem is not flexibility -- the systems are in place, and must inter-operate. IP networking for these systems is not completely in place (some use serial communications). The cut-over to IP networking is still on-going, and some places use parallel serial and IP networking.
And, of course, 911 operators get ANI/ALI (automatic number identification, automatic location identification) data for home phones (ALI by database, usually), and the mobile needs to be incorporated in such a way as not to confuse the dispatch operators.