To add a little more detail to Robo's answer our recent experience, for an 8am tour on a day the park opened at 9, was as follows.
We went through bag check. We were directed over to the left hand side of the tap stiles. We were asked what tour we were there for and at what time and then invited to proceed through the tap stiles (those with dining reservations were more actively checked against a list). We joined the crowd gathered by the left tunnel under the train station and were all let in together at between 7:45 and 7:55.