When I was there two weeks ago and staying offsite at Disney, we got to Universal at 7 AM. They let us in the turnstyles with the onsite guests but once in POE I told the TM that we were offsite guests and he said, "Do you know where Jurassic Park is?" when I answered yes, he told me to head that way. It was kind of a fun experience wandering through Marvel, Toon Lagoon ect when there was no one else there. It was literally my cousin, myself, and two other early birds making the long trek around the park. Once in JP there were TMs waiting for us and they handed us tickets to mark our line status and then put us in line. Around 8:15 or so, a couple TMs came out and started counting us with a clicker(there were maybe at best 20 of us in line). Surprisingly enough, at 8:30 AM they came back out and said, "Welcome to the Wizarding World of Harry Potter" and lead us over the bridge into Hogsmeade half an hour early. It was an easy process and all ran like practiced clockwork.
However, I do stress that it was getting there early that helped make it run so easily. My aunt and uncle didn't get to IOA until 11 AM and they were in line for 35-40 minutes in JP to get into WWoHP.