There could be hundreds of reasons, which is why you prolly didn't get replies.

What kinds of news sites are you referring to?

-- Major sites? If so, their stories are similar but different to one and other.

-- RSS feed sites in specific niches, that all look like each other?

-- Niche sites in a given vertical with lots of content but that also incorporate news feeds from the major news outlets?

-- Other?

Basically, the more clear and specific the opening post, the more likely it is to elicit clear and helpful answers. ;-)

Major sites - Hit the nail on the head! Am talking the big 3 which everyone visits. I have read the same versions of storys on several sites.

How "Different" are they?

Just a few words?
Just a few sentences?

OK, well the major news sites, e.g., cnn.com, run many of their own stories, have their own unique structure, nav, page titles, features, etc. Yes, they, like other news organizations, take syndicated content from the wire services, but that is a relatively small percentage of the news site's overall presentation of content.

And even then, sites with lots of their own original content etc, can port in feeds and/or syndicated content as a part of their mix, with little or no worry.

Beyond that, a lesser known aspect of at least some SE's is their ability to profile certain kinds of sites, and it would not surprise me at all that news sites fit a certain kind of profile that further ensures their stability, generally.

Add to that all the other factors that go into algo's, like number and quality of backlinks, and it starts to be relatively easy to see why a major news site might rank well.

There can also be measures in place to assess currently hot, newsworthy content and topics, and different high profile sites may have different editorial slants, so showing them would be valuable to include.

Besides,I don't believe that sites that are above a certain threshhold of importance (and/or authority) are subject to the same kind of filtering. There seems to be a point at which an immunity appears to kick in.

So the search engines are manually added to a database of some kind! Is this what you are suggesting?

I see time and time again news sites that have the same storys but they all rank very highly - How comes they are not being done for dupplicate content?

Because although lots of news sites feature the same story, their whole sites aren't duplicates of each other.
For instance, I've got an article dirctory and the majority of the articles are featured elsewhere. However - because I'm choosey and don't accept any old article, my page rank and alexa rank have both been constantly rising.

A large number of news sites are being hit, but, can you imagine how big the task is, and, importantly, how to identify which is the authority and which is the dupe?

How to identify which is the authority and which is the dupe?

My experience shows that its a first come, first serve basis from the get go. As time goes by, the authority will usually gain natural links which tends to trump the dups.