Yes,it is park to park which would allow you to ride Hogwarts Express. If it were me, I would take “a chance” depending on time of year if you will even need Express Pass. If you do once you get to the parks, purchase it at the park on a pay as you go daily basis. Or consider staying at one of the on-site 3 Universal hotels which include Express Pass. So for 1 night of one of the 3 on site hotels, you can get 2 full days of EP. Caution, the hotels are so convenient and EP is so great, you will be spoiled!