in 10 years of working at a small airport serving commercial airliners never.
ILS is a pilot interpreted landing aid, ATC has no obligation to follow the plane once established on ILS. ATC has the responsibility to vector the plane to such a position and altitude such that the plane can intercept the localiser and glide slope. At airports doing dependant ILS approaches ( 2 aircraft on 2 parallel runways ) ATC follows the distance between planes, not the altitude/glide slope. If providing radar services the ATC vectors the plane until established on the localiser then it's the crews responsibility to follow the ILS procedure.