If I had to guess, I'd say transporters are probably used as an alternative means to mass transit, supplementing commuter shuttles and high speed rail. For example: on a particular trip I might leave my house and walk to the nearby CTA station, take the high speed Green Line train downtown (an eight minute trip) and walk to Union Station where I can either hop on an Amtrak train heading to any other location (Amtraks now run through underground tunnels at 550mph using turbolift-style linear motors) or I can get a transporter pass and beam to any other transporter station at the major transport hubs at any city in America.
In this case, I use Metra's transporter and beam to the Amtrak station in Pittsburgh, then take one of the regular commuter shuttles to the University to buy a book from the local bookstore. The bookstore doesn't have it, so I head back to the Amtrak station, beam over to Philadelphia, take another shuttle t the U-Penn Bookstore where I finally find it. Then beam right back to the Chicago transporter pad at Union Station and take the Green Line back home.
Total trip time: Two hours, twenty minutes. And most of that was spent sitting at a stop waiting for a shuttle or a train or waiting for my turn at the transporter.