It's a probability that a unidirectional microphone was used on stage, facing the audience, to place the audience sounds into the soundtrack.

As Mojo suggested, the more accurate would be to have the audience surrounding the listening position, but this typically takes one omnidirectional microphone in the audience, which is a tough task, especially in a large venue.

Mojo - I will check the CD tomorrow to see if it was remastered, but that still would not have an effect on microphone placement.