From Memory the whole point of the ramps was to maintain subsonic airflow over the compressor (0.5 mach I seem to remember as being the figure always quoted) regardless of Aircraft Mach. The ramp movement was scheduled using a small pitot probe in the intake itself sensing purely intake airspeed.
The intakes did this on the GR1 despite having the ramp cb's pulled because the unmodified intake profile was sufficent to slow the intake air down (upto, again from memory, about 1.5 Mach aircraft speed)
No idea about GR4 Ramps