1. the camera doesn't follow the bus because the target tag is attached to the camera null so the null is targeted but the camera isn't lined up with the null's z-axis - easiest thing to do is put the target tag on the camera directly. Next problem is you are targeting the bus null, which does not move. Target the front or back of the bus instead (you can't target the joint either since it is also in a null which does not move)
2. the joint section jumps because the Constraint tags which control the location of the Joint splines are being evaluated after the align tags so the bus parts move but the joint bits don't move until later. Increase the priority in the Constraint tags to something greater than the priority in the Align tags (1 is enough)
3. you are controlling the position of the bus by the Position in the Align tag of the front part of the bus. You can't add more points because the spline is remains the same length. You could add more keyframes to the Position parameter but it's really hard to do that smoothly, it's easiest to use few keyframes but to control the speed of the bus between the keyframes with the F-Curve.
Check it out
