Besides the technical problems, there are a lot of liability issues that come up. Unfortunately most places now are so conscious of potential law suits, that gaining the necessary permission is difficult. I don't recommend the stealth approach, just too risky. In the series I did, I had permission to be in the factory after hours.
First, a caveat: I don't like shooting "industrial nudes," any more than I like shooting "environmental nudes." It seems contrived to me. And, unless you have some really extreme ideas waaaay out there, it's clichéd.
With that caveat: I was once asked to shoot an outdoor series with a woman who wanted to use the photos for promotional purposes. (No questions, please.) I took her down to Wall Street early on a Saturday morning -- cobblestones, monumental architecture, great light, no people. At least, that was the plan.
We started in front of the Cocoa Exchange. It's a landmark building on a perfect location. The location was ruined by a big Mack truck -- work crews gutting the old Harriman Bros. bank building had cordoned off the surrounding streets. We shot a couple of rolls of her in front of the Mack truck.
http://www.pbase.com/studionyc/image/31450186
The truck belonged to a Saturday crew of construction workers. The Saturday foreman was an electrician. He came over and took an interest (guess why). To make a long story short, the crew adopted us, gave us free run of the site. We shot a half-dozen rolls on Exchange Place,
http://www.pbase.com/studionyc/image/31450254
and a few more in the hopper of a backhoe
http://www.pbase.com/studionyc/image/31450250
and still more inside the building.
http://www.pbase.com/studionyc/image/33046618
There's a moral to this story. Had we tried to arrange this shoot in advance, it never ever would have come off, for all the reasons Craig noted, and more -- the entire work site was paralyzed by the collective libidos of a hundred stunned drooling (but entirely respectful) union guys.
BUT
If you find a place that you want to do a shoot like this, and just show up with your model and a couple of assistants, odds are the guys working the site will be MORE THAN HAPPY to let you in and shoot. Especially if it's a Saturday shift, when the bosses are more likely to be away. The foreman of that job told us we were free to come back any Saturday.
He also asked me for prints to prove to the weekday laborers that it really happened. I was mobbed when I brought them by the site a few days later. It's not my gig, but it was a lot of fun.
Sanders