A friend of mine is retired from working in forestry for over 30 years (and the air force before that). He's always told me that a fire is always worth the risk of a forest fire because forest fires could be put out (he'd have been unemployed without them he says) but you can't be brought back to life. He also told me that you still need a bit of common sense with your how and where you build your fire. More importantly to him since it's not always possible to set a signal fire in a perfect risk free area is once you get rescued (no matter by who), call the forestry department when you get back to civilization and tell them about the fire and where you were. They'll send somebody out to check it out and put out anything still burning before it gets out of control.

Now Alberta and Arizona are very different and I don't know how much that has to do with it and the article doesn't say what type of signal fire they made (unless I missed it). They could have set a tree on fire intentionally as a signal instead of doing it properly.

Addendum: Personally I've never heard of a search operation waiting like that (though that's just my experience. I'm sure it's happened before and will happen again). I could never live with myself if I were the search manager who made the call to wait if there were a chance this fire wouldn't have been so unstoppable had they acted immediately...or worse, if somebody died because they hesitated.