Gents and ladies,
The ICAO (and generally accepted rule over the planet) is 250kts or less at or below 10000ft. Usually the the speed limitation does not apply to military acft (as they seem to be a law unto their own) or unless it is required by acft concerned due to configuration, etc. So yes wherever you are flying it is is best to request permission and say due to operational requirment. The same goes for holding speeds.