Sorry, but there isn't much you can do beyond what you've already done. Soundtrack Pro's Noise Reduction works kinda-sorta okay on consistent background noise like the noise from a transformer.
But your audio has all sorts of issues: people yelling, PA, echoes.... you're stuck. I hope it isn't so bad that the background noise makes the interview totally inaudible, because you just have to live with it.
Okay, that's not quite true. You'd have to buy a third-party plugin like Soundsoap. You'd get an improvement, but not perfection.
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA