Wont be any problem for the pigs. I dont know if its still there but on
www.pigsinfrance. there was a whole thread on a sanglier piglet that had either been orphaned or separated from her family, who grew up with horses on a farm (the piglet was wild) and who has now given birth herself to a litter, still protected by the horses (and their owner).
Either way, dont let the horses get anywhere near the pig food if its a proprietary one, as it is dangerous to horses.
So glad you have found some land. A bonus will be that the horse owners will be able to keep their eye on your pigs and vice versa.
Now all you have to decide is what breed.