After placing every file in its corresponding folder, you need to add the Replacement Mutator to your game. Either by doing so via Menu (don't forget to configure which vehicle you want to replace!) or via Commandline/Votingconfig in your server.ini: (Example for GunShip)
ucc server ONS-Torlan?Game=Onslaught.ONSOnslaughtGame?Mutator=HL2MonstersLite3.MutGunShipReplace -nohomedir
Otherwise, like always, add the Packagename you intend to use on your server as ServerPackage line to your ini. Example:
I think since you're only after the Vehicles, this should be enough. Otherwise you might need to add HL2Monsters too.