No tyre inserts will be provided with the tyre sets you'll get from the organizers. You are allowed to use any tyre insert you'll want. There's a link in english:
http://www.vueltarapida.automodelismo.es/indexeng.html
Feel free to contact them for further details. I'll answer any question you'd have, but please have in mind I am not the organizer, so I only could talk about what I heard and what's published at spanish websites.