From what I read on the wiki and have seen in the frontiers there are definitely caravans. They are required for keeps to progress past level 4?(not sure) So they need to survive their journey, killing them would benefit the realm due to keeps not upgrading. This is from memory so please correct if wrong.
"If you claim a keep it will upgrade automatically and it doesn’t cost any guild bounty points. It will only upgrade to Level 4. After that it needs caravans to reach the keep and to deliver supply goods to the Outpost. Each caravan has 2 guards to protect it. Caravans are neutral to enemy players. If you kill a caravan you will get some bounty points, XP and coins and you will stop the keep from further Upgrading. Caravans also drop Phoenix Claws. These can be used to buy timed buffs for XP, Rps and also Stealth Lore Potions. If the keep already has reached the max Level it will start downgrading if multiple caravans didn’t reach it and killing caravans will also damage keep gates for an amount.
Caravans start either from the homeland border keeps or from the teleporterkeeps if an enemy realm has claimed keeps. Example for Hibernia: Caravans for Hibkeeps start from Druim Ligen and Druim Cain. If Midgard has keeps claimed in Hibernia, then caravans for those keeps start from the MTK, if Albion has claimed keeps in Hibernia, caravans start from the ATK."