Are you asking about reloading a subscribed list? There isnt a way to force reload a subscribed list.
If you are going through the trouble of trying to reload it via REST, you could just upload the list to the MWG as a "static" list instead of using it as a subscribed list.
This way the download of the list is dependent on your application which creates and uploads the list, rather than being dependent on MWG downloading the list on it's schedule.
Exactly that was my plan: forcing the reload of a subscribed list.
Thanks for the answer - I already feared that it would be exactly this answer.