When I was an explorer, the private security did the inside stuff. Like getting rid of drunks, mosh pits and so on. And LE did the outside, traffic direction and close off the streets. The only time LE went in was if the inside security got over whelmed. As for monitoring the security air, most of the streets are blocked off, I guess you could always walk as close as you could and use the close call or signal stalker. It's in the middle of the DTC so you might get a lot of other stuff, but it's worth a try right?
Just to let everybody know, I went to Coors Amphitheater but never got the chance to try to find any interesting communication. (i.e. Band crew communication, etc). Due to traffic and long lines I already missed the first band. My wife would have been pretty upset if I delayed us any more if I was tinkering with the scanner. =(.
Next time I up there, which should be before the summer it out, I will try again.
>I'm not too sure who RRI is and was unable to easily find any information on an RRI in the Denver area. <
RRI (Radio Resource Inc) rents radios out for various events, like concerts, Cherry Creek Art Festival, Grand Prix, etc. They use normal business freqs, so doing a search "on scene" will probably be your best bet. They have equipment in VHF and UHF bands.