I imagine they have a few tools at their disposal.  But as Mr. Schulenberg already noted, one of the main methods is via satellite link from the location back to the "studio". Rather than an Internet connection, they are likely direct connections from truck to studio, where any necessary mixing and real-time editing is performed before broadcast.

A search for "Satellite News Gathering" (SNG) may provide you some additional helpful information.

Regards,

Ed