I haven't read the entire thread (14 pages!), but...
Generally speaking, the news is about what is happening now. We're not talking about the philosophical notion of an infinitesimally small amount of time, we're talking of a definition of "now" which is useful to human beings in everyday life.
Headline English uses the simple present or incomplete verb phrases because headlines have to convey a lot of information in a very few words.
In the main article, though, you will find an abundance of present tenses, whether simple, progressive or (very often) perfect.
I don't know if these have been tackled before, but let's look, shun, at the examples you give:
Ex1: Several groups, including the National Abortion Federation and the Center for Reproductive Rights, plan to challenge the measure in court as soon as it is signed into law.
This is indeed not the usual formulation ("are planning" would be expected), but the use of the present simple here emphasises the fact that it is a long process. They may not actually be sitting together planning the whole thing as you read the report, but generally they do quite a lot of planning. This would be unusual in most domains, but in the domain of journalism, it's quite normal. You will, however, often see this in the present progressive; both forms are possible (and common).
Ex2: The reality remains that Tung will be at the helm until and unless Beijing leaders think otherwise.
"Remain" is one of those verbs that is very often used in the simple present where the present progressive would normally be used. It indicates a state of affairs rather than describing an action.
Ex3: The 30 new candidates come from around the world, from Australia to Zagreb, Vietnam to Venice, and on the whole follow John Paul's conservative bent.
Again, this is a state of affairs. "Come" is always used in the present simple when used to indicate someone's origins: I come from England, but I live in Germany.
Ex4: The Israeli government says it needs the new buildings because of the "natural growth" of the settlements. However, the "road map" does not take that into account in its blanket building freeze.
When "say" carries the meaning of "be of the opinion of", it is used in the present simple. It indicates that whenever you care to ask them why they need the new buildings, they will always say, "Because of the natural growth of the settlements". "Need" is a verb that is only seldom used in the present progressive and again indicates a state of affairs, not an action. "Take into account" is very often used in the present simple, but especially when, as here, the subject is an inanimate object -- it is not performing an action, it is simply there, and whenever you study it you will notice that it doesn't take the blanket building freeze into account.
Ex5: A final vote in the U.S. Senate B remains before Congress sends the Partial-Birth Abortion Ban Act (S. 3) to President Bush for his signature. The bill represents the first direct national restriction on any method of abortion since the Supreme Court legalized abortion on demand in 1973.
We've already dealt with "remain". And with "represent" we have, once again, an inanimate object.
Ex6: Nevertheless, some Democratic senators who oppose the bill, including Sen. Barbara Boxer (D-Ca.) and Sen. Tom Harkin (D-Iowa), prevented the vote from occurring before the Senate began a 10-day recess on October 3. This means that the necessary Senate vote cannot occur earlier than mid-October.
Pushing a bill through takes a lot of time and effort. During this whole process -- and, if the bill is passed, for ever afterwards -- some senators may oppose it. If the present progressive were used here, it would mean that they are opposing it now, but they might not have been opposing it on October 3rd. The author wishes to make it clear that the opposing was happening on October 3rd, it is still happening now and will continue into the future. "Mean", in its usual sense, is another verb that is seldom used in the present progressive -- we ask "What does this word mean?", not "*What is this word meaning?"
Ex7: Seventy percent of Americans support a ban on partial-birth abortion.
See "oppose" above.
Ex8: Italy's U.N. Ambassador Marcello Spatafora, whose country holds the EU presidency, moved between the two groups, sometimes with the British or French ambassadors alongside......
This describes a state of affairs, not an action.
Ex9: The U.S.-backed "road map" plan requires a freeze on construction in the roughly 150 Jewish settlements in the West Bank and Gaza Strip. Palestinians hope to establish an independent state in the two territories, which Israel captured during the 1967 Middle East war.
With "require", we again have an inanimate object. With "hope" we have a state of mind which is not limited in time; the Palestinians hoped in the past, they are hoping now and they will continue to hope. We only use "hope" in the present progressive when the hope is expected to be short-lived: "I am hoping for rain tomorrow" is OK because, whether or not it rains tomorrow, the hoping will be over the day after tomorrow.
Ex10: It warns that "a new boom and bust is in the making and will likely start to show up at the end of next year or the beginning of 2005".
This is quite normal in journalism; it's like "say", in that, for an extended period at least, any time you go to "it" (whatever "it" is), "it" will warn you of a new boom and bust in the making.
Most of these examples are actually standard formal English in any domain; only a very few appear to break the rules, and they do so with good reason. But if an action is actually taking place at the time and is clearly (or hopefully) of limited duration, the present progressive is often used. Here are some random examples I found:
"The five permanent UN Security Council members and Germany are meeting after the EU said it had failed to convince Iran to stop enriching uranium."
"They are demanding a complete ban on fishing, arguing that there would be plenty of alternative areas to satisfy fishermen and women."
"West African leaders are meeting in Nigeria to discuss the crisis in Ivory Coast."
"The Bolivian government is sending 700 troops to a tin mine as clashes between rival miners enter a second day."
"The EU is placing a tariff of 16.5% on leather shoes imported from China over the next two years."