I know its another part of the world but we have "air patrol's" here where mirages go out at FL300 and then turn off their transponders and then come back and turn them back on, and whilst by the book it is the military's responsibility to separate as a civil controller we still do all we can to avoid the military traffic we see on the radar. Sometimes it's hard not knowing the intentions of the mirage but still we avoid the aircraft and certainly would never knowingly descend the aircraft through the radar observed position of the military aircraft. Dunno if this is relevant but thats my 2 cents worth.