I presume "atraco" is a way of saying that it is illegitimate and predatory, morally if not legally a robbery. I would be inclined to call it the "great oil robbery", because the expression "great X robbery" is a set phrase (derived from the Great Train Robbery in Britain in 1963); by putting it this way, it will be clear that the term is being used metaphorically. I think it really needs a verb in English, so I suggest "perpetrated".

For "las grandes petroleras", it is tempting to put "Big Oil", but this technically means the five supermajors, and we can't be sure that there aren't other oil companies involved (in fact I think there are, such as Anadarko). So I'd just say "major oil companies".

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Note added at 28 mins (2013-12-01 13:35:35 GMT)
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Here's an example of the expression "great oil robbery", used to refer to predatory and extortionate practices by the oil companies:

http://peakoil.com/alternative-energy/the-great-oil-robbery

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Note added at 5 hrs (2013-12-01 19:02:36 GMT)
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I've just read Pablo's answer, with great interest, and this has led me to do some more research. The idea that "atraco de Wall Street" refers to a metaphorical raid or armed robbery OF Wall Street by big oil is inherently strange, and I am quite sure this is not the meaning.

How Big Oil could or would carry out a robbery of Wall Street is difficult to imagine anyway, unless it is by manipulating share prices or something like that. In any case, if it meant that it would normally be "atraco a Wall Street", not "atraco de Wall Street". And this reading is also difficult to reconcile with the Spanish original, because it leaves "y las grandes petroleras" hanging, without a syntactic function (it surely doesn't mean a robbery of Wall Street and of big oil, since big oil is presumably perpetrating the robbery).

I think the source text makes sense. The function of Wall Street here is as an accomplice, not a target, of the oil companies. They want unregulated, unrestricted exploitation of reserves by fracking, for which Peña Nieto is proposing to offer an opportunity in Mexico, and Wall Street (the banks and hedge funds) provides the necessary finance (a vast amount of investment is needed). So as I said, it's a "robbery" perpetrated (on Mexico, in this case) by Wall Street and the oil companies in partnership. All this made possible by Peña Nieto's proposed privatisation program, which is what "el atraco petrolero de Wall Street y las grandes petroleras articulado por EPN" (see first source below) refers to. In other words, what Peña Nieto is proposing provides the opportunity for the major oil companies, financed by Wall Street, to "steal" Mexican resources (from a Mexican perspective): in that sense, "está articulando un atraco".

I've been reading these sources:
http://www.jornada.unam.mx/2013/11/28/opinion/030a1eco
http://www.noticiaspia.org/explotacion-de-fosiles-no-convenc...