The URLConnection.Error event only fires when the connection just couldn't be made at all. The description that we had in the docs was wrong so I have just updated it. I suspect in most cases that's all that really matters.
However, we could be mapping the most common errors to our own special set of URLConnection errors. Perhaps an enum?
So I have created a case in Feedback for this. Please feel free to sign on to it, add your own thoughts, etc.
While I can't make any promises about when we will do this, given that URLConnection is relatively new and is part of API 2.0, I can say that I'd like to see this get done sooner rather than later.