They mentioned earlier, that "Frankfurt", "Gibraltar" and those nodes are not actually located in a specific province. On the map it displays them on specific provinces, but actually, these names refer to an entire area around those provinces. Who owns the name-giving province, does not matter so much. You might now own Frankfurt province, but still control 99% of the trade in the Frankfurt node because you just are that awesome.
So it's a bit like the CoT areas in EU3, but the CoT does not exist any more, it's just a disembodied set of numbers for a specific area.