I always knew a train station could be used to "borrow" someone's track in order to finish your assignment, but is it also allowed to "borrow" someone else's trains and count them as your own for the longest path? In the Dutch manual, it's debateable. All it says is the longest path is the longest uninterrupted route, but then again, that's where stations come in (right?).
If I remember this right, the English rules of TTR:E specifically mentions that stations are for completing tickets only and are not used when calculating the longest path bonus.