Hi @AJönsson1 
The “Subscriptions” CRM object-type is part of HubSpot’s Commerce offering -- it’s completely separate to a Contact’s “Communication Subscriptions”. As far as I’m aware, it’s not currently possible to configure a webhook subscription based on a Contact’s “Communication Subscriptions”. However, I could be wrong.
Unless someone else chimes in here, you may have to consider a polling solution that would call HubSpot’s Subscription Preferences API.
I hope this proves helpful. Please let me know if you have any follow-up questions.