Yes, this was the exact same case when we went in 2009. We did the DP with the Fourth of July fireworks (on July 3,) and then Spectro (at that time it was Spectro) was at 10:00 and it was an EMH night.
Let me WARN you....... if you think you're going to leave the DP and go find a spot for the MSEP bring your suit of armour! They were routing people out of the park through Tomorrowland, so it was MOBBED all around the DP and we could barely even get out of the terrace area. Then, the CMs were trying to MAKE us go with the flow out of the park. We said we were staying for EMH, and they said we'd have to go with the crowd because it was too dangerous to go the other way. They said we could either go out to the front of the park and then come back in to watch Spectro, or go with the crowd and then take a left to go through Fantasyland and around through Liberty Square to find a spot.
At that point it was already 9:30 and we were worried we were going to miss Spectro. We waited it out a little bit, and then another CM let a group of us go toward Main St (past the Plaza and Casey's) so we could cross over to Liberty Square/Frontierland to find a spot for Spectro. They said it should have been clear enough by that point so it was ok.
Let me tell you...I have never been so afraid for my safety. It was a MADHOUSE! People were knocking over strollers and wheelchairs, pushing, screaming.... it was nuts. Luckily, we were 3 adults, so we chose a meeting place, and tried to individually duck and weave until we could get across. It took us 45 minutes to get from the DP to a spot for Spectro in front of Diamond Horseshoe. Due to the madness, Spectro started VERY late (I think it was closer to almost 11:00.) I just wanted to give you a heads up in advance. Otherwise, it was a wonderful night and we had a blast, along with a crazy story to share