I have stayed at BCV and decided last minute to go into the park for Illuminations. This happened to me twice, but it was very late.
I got to the gate at about 5 of 9, just before the talk before the torches are blown out.
I tried to find my pass and the people at the gate had just waved me in. I don't know if they recognized me or just didn't want to see me empty everything out of my fanny pack.
This was before the security checkpoints once, but after the 2nd time. I had already been checked by security so I guess the CM's knew I had nothing in my pack.
But don't try it unless you want the embarrassment of being turned away. The bridge at the entrance is a fairly good view for the high fireworks if you can't get into the park.