I've worked with two 911 computer-aided dispatch (CAD) systems (both from Motorola, but varying wildly in quality and provenance) and neither has any such thing. Both don't directly handle phone calls either, however. They have APIs that interface to the phone and radio systems to move traffic between. In the case of the PSAP (a Public Safety Answering Point, aka a 911 call center) I support the caller is being handled by one system that passes the calling number (ANI), static telco-provided geolocation/metadata (ALI), and live GPS geolocation to the CAD system. Aside from these defined interfaces the systems are separate islands and function (and, more importantly, fail) separately.

Edit: Text messages are handled by a third-party with a SIP-based interface (running over a VPN across the Internet) to the phone system. My guess would be this is how video will be brought in. These third parties are already positioned in the telco system to handle this effectively (from a regulatory perspective).