When we used our vouchers, we did have to check in with the CMs probably 40 minutes before the show. Maybe more, actually. Then we had to be back to stand in line by a certain time. The voucher people stood up near the "entrance" to the theater...the normal people lined up behind/to the side of the theater. They got there when they wanted to.
We were let "in", but it's not "in" anywhere, it's just more line, but it makes it look like you're going in! We actually were let into the theater LAST, but put in the "orchestra" section, the ground floor, where we got to sit. Awful seats, just awful. Somehow preferred seating meant...line up FAR longer than standby people and get worse seats...
I'm sure it's been done differently by different CMs on different days, but that's how it was done on "our" day.