This usually works with a clapping at the beginning of both the video and the audio record which then could be synchronized. But as you mostly have the audio source from the video file and the clean audio file from the PA recording, you could watch out for sudden peaks to find marked similarities on both audio tracks. Then its more easy to align both files.
I'm pretty sure there is no script for such cases but it could be done per peak matching. Maybe its possible to find a certain sequence of peaks in two different audio files. But I have no idea. Kawa, mpl, 2beat etc. could answer this.