I'm pretty sure Julio's statement in the very next panel is a lampshade on the fact the *won't* have the defences rebuilt: "It's not like they're gonna get invaded before they can repair it, you know".
Having said that, we know they did have some functioning catapaults during the attack:
http://www.giantitp.com/comics/oots0451.html
I suppose it's possible the delay to firing the catapaults Redcloak is talking about there is because they were having to do a fast repair job on them and only just finished?