Yes you can resupply people when the commander doesn't tell you. You can't keep doing it though because you have an energy bar, so you can't just keep resupplying someone because eventually the energy will run out.
you can sure
the e3 2010 demo seems to be recorded by a newbie though so we have no idea based on purely that if it changes. commander and automated teammate recordings imply it can be ordered but that guy spends the whoile round too low on ammo so his current objective appeared to be resupply himself.
however 1-2 exp per hit 10-15 for a kill 30exp for resupplying someone and we have no idea what exp he got for stopping the fan as the cutscene overrode the screen. the objective wheel seem to say 25 for a command post.
these numbers are largely irrelevant NOW as the game is still being balanced and tuned. but as you can see resupply is rewarded and objectives are rewarded. the earlier bomb defusal map had objectives as a couple hundred points so either these objectives were all mediocre or the numbers changed.
it doesn't help the player in the e3 2010 vid seemed to be confused 90% of the time. not their fault i know but a vid straight from splash damage would have been far more useful.