It would be fairly easy to overwrite, however I think there is some confusion that should be cleared up first.
First, the toArray() method you are calling in this case is on the Collection which is the object which is returned when you use get() on your model.
With that said, you can add the following to your Location model to return a custom collection...
public function newCollection(array $models = [])
{
return new CustomCollection($models);
}
Then you write the new CustomCollection class with appropriate namespaces just to make sure it gets auto loaded fine, have it extend \Illuminate\Database\Eloquent\Collection and then you can proceed to override the toArray method.
However, it feels like you randomly selected this toArray() as a proper candidate to perform your logic just because you are already using it. You should think about creating a new function which calls $this->toArray() to grab the results and modify them as you need and return that.
If you need this same functionality on other models, just keep adding that newCollection method where needed.
This is also in the docs as well, might be worth checking out...
https://laravel.com/docs/5.2/eloquent-collections#custom-collections