Here's the way it works. It depends on the which environment you are in. If you are in a terminal area (within 5 miles of the terminal), you will likely have a primary target but if you are responding to their transponder inquiry, the primary target is insignificant and unimportant given most transponders now send altitude information. When you first contact approach, you are given a squawk code and they enteryour tail numberIf into the compute. If you are enroute (cross country) then those radar sites usually are very spread out and primary returns aren't always generated. In fact, in some areas of the country, they cannot even pick up your transponder unless your are 3000' above the ground level.

Almost every plane has a transponder in it. For acess to certain airspace it is required.

Most VFR flights "squawk" 1200 unless you opt for "flight following". They typically do not file a flight plan and if they do, they can deviate at will. The only thing the flight plan is used for is to find you if you turn up missing. There is simply no way to distinguish between planes on a VFR squawk.

The Flyte Comm information provided above was I believe a little in jest. I do not believe they could actually pick up much meaningful information from a private flight. Even IFR flight plans typically just list the plane, tail number, air speed, flight route, departure time, number of people on board and Pilot's name. No passenger list or anything else. If it is a VFR flight, then they could not pick up any information simply because there is no way to distinquish which plane is which.

I believe Flyte Comm picks up a feed from the FAA and puts it into a format people can access. There are other companies that provide the same or similar service, itracku, trip.com, flightview, etc.