Verify integrity of the game from the launcher, should repair the file (I think) Anyway, how on earth did you delete the file? Couldn't you have just restored it from the recycle bin or something? EDIT: What Nadeox said.
Actually it's this: https://support.steampowered.com/kb_article.php?ref=2037-QEUH-3335&l Steam will re-download any modified/missing files from the game's directory.
If all else fails, back up your mods and re-install BeamNG All you gotta do is go to the steam settings, uninstall all BeamNG assets, and install BeamNG again. And how did you delete your bus files?