Great news that the hog population there has increased.
If you have a hog box with an internal passage, you could try reducing the height – especially where/if there is a part of it where the animal is required to do a U turn – by using bricks. The hogs being quite short seem able to negotiate such an arrangement, but the cats, seem unable to turn when they have had to flatten down to get through the gap over the bricks.
You could also try putting an obstacle either side of the entrance so that the cats don’t have the option of entering at an angle (for instance if they have to turn immediately right or left after going through the doorway).
Hopefully if the cats know they aren’t going to get any food, they won’t bother to visit.