Don't expect another passenger will help you as they naturally worry they will be the next target. Especially if they are using the bus daily.
Watch it for this bus PPD P 157. If you wish to see the route you may refer to this link. Unfortunately is in bahasa Indonesia.
You may be friendly with other passengers but don't let your guard down. If your bag has zipper make sure the bag never lost your sight. If you are wearing backpack maybe you should put it in front of you. They can use cutter to open your bag and take whatever they can have.
Enjoy Jakarta but always be careful!
