Car manufacturers get the last say on how their cars are used on any media; and they typically go with licence agreements of some sorts.
The licencing is typically done on a set time frame (which is why most car games that uses real cars does get taken off of stores like 5-7 years later.).
On Fortnite, revenue sharing is done between the IP owner and Epic Games based on how much the said item sells. Since they can this item launch as a limited time sale; this gives a big playerbase an incentive to buy it.