The 45 minutes (or 60, or 75, depends on the source) is a rule of thumb for "regular people." It's also usually correct. However, your body doesn't go catabolic if you train for 45:01. It's just that generally beyond that timeframe your body starts producing cortisol, which is a catabolic hormone. How much is released and how it affects you is dependent on a lot of factors.
I used to train for 90+ minutes of weightlifting, plus football practice, plus running, and still gain, and I'm pretty sure those guys can, too. It's a combination of body adaptation, nutrition, the kind of work they do, etc. Usually overtraining isn't brought on by just training a lot; it's training heavily while not supplying your body with what it needs.
I probably didn't say it the right way the first time around, though. They don't "live in the gym" or work out all day, but they do have a heavy training volume. That's why when you see the program a professional uses in a magazine, it's generally a bad idea to try and follow it. You're not used to the training, and especially to their training volume, so following their program isn't appropriate.
