Thanks MB.
By an "operating twin that is 'on task'", do you mean police work? If so, isn't this is the exception rather than the rule; clearly it has priority over traffic that isn't on task, hence transiting traffic having to hold (in an orbit, not hovering!) or accept visual separation. Police may have to hover at a specific point in order to complete the task. For other commercial or private drivers, I can't think of a legitimate reason to have to hover on a heli route, especially in a single, even if on a film job?
On a slight aside, many moons ago I was hovering at Bedfont, waiting to cross Heathrow. Tower asked me to maintain a tight orbit instead as apparently I was invisible to radar in the hover (presumably primary, not secondary).