When you spawn (When you join the server, and THEN spawn), the vehicles get downloaded and placed. When you spawn after that, it won't do anything. I supposed that if you die, that the mods are still replaced? (It's a client-side script, so it will work for all players as soon as they join) 
PS: If you remove line 60, it will replaced as soon as any player spawns. (And if it wouldn't then it wouldn't matter anyway)