Al there are two types of braking systems similar to what you describe; The first is magnetic track brakes which is probably what CTA uses, they are common on European trams and some narrow gauge railways. Basically you have a long brake shoe mounted on the frame of the tram that is clamped by magnetic attraction directly to the railhead. This is typically an emergency braking system because it rapidly decelerates the railcar. The other system is an eddy current braking system and is used for emergency braking on highspeed trainsets like the TGV and ICE, this works like a reverse linear induction motor working against the rails, this is used only in an emergency as it rapidly heats the rails and can cause kinks and other disturbances in rail alignment.