A unit can assault the occupants of a transport if it destroyed that transport in the shooting phase, yes, but it has nothing to do with being on an eldar jetbike. Page 67 of the rulebook:
Note: remember that all models in a single unit fire simultaneously, so a squad cannot take out a transport with its lascannon and then mow down the occupants with their bolters. However, if a transport is destroyed (either result) by a ranged attack, the unit that shot it may assault the now disembarked passengers, if it is allowed to assault according to the assault rules.