Would the author care to mention the name of the study, who it was performed by, or even (*gasp*) provide a link? Otherwise a reference to "one recent study" has no credibility whatsoever.
The OP was quoting from the NY Times article that was linked to in the post. There are even quote marks in the post to indicate that. The times article gives a link to the study: http://www.people.hbs.edu/wkerr/Kerr_Kerr_Lincoln%20Feb2013.pdf .
One could blame the OP for not providing some personal commentary on the article that he or she quoted, but you can't blame the OP for not citing the study. On the other hand, one can and should blame the reporter who wrote the Times article for not summarizing the study better.
The study says that hiring of "young skilled immigrant employment, where young workers are defined as those under 40 years old" is correlated with "expansions in other parts of the firm's skilled workforce". And "a 10% increase in a firm's young skilled immigrant employment correlates with a 6% increase in the total skilled workforce of the firm." That seems logical -- a firm on a hiring spree will look for engineers from many sources. But it doesn't say anything one way or another about why the companies are hiring the immigrant workers. Is it because there's a shortage or because the immigrant workers will work for less money? The study does not say. Moreover, the study does not seem to consider that hiring of foreign workers means that fewer native workers are hired who would otherwise be hired, even if there is an overall increase in the number of native workers hired.
And I wonder how the researchers who published the study would deal with companies who lay off much of their IT staffs and replace them with contractors through Cognizant and the other large consumers of H1-B visas. The company who laid off their staff does not directly hire the H1-B visa holders, but Cognizant does. Naturally, Cognizant hires support staff and some native engineers to support the buildup of the H1-B staff. This conforms to the study's conclusions, but the net effect is that many native engineers have lost their jobs.