Actually, I'm one of those who thinks the Constitution means exactly what it says. The clause you quoted has absolutely nothing to do with this case or any other case involving a local government involved in an eminent domain proceeding. The clause you quoted deals specifically with the U.S. Congress -- it gives Congress the power to exercise authority over any lands that are purchased by the U.S. government (with the approval of the state legislature) for any of the various purposes you listed.
For a real application of Constitutional law to the case in point I'd recommend that you read the Tenth Amendment, along with this specific clause in the Fifth Amendment:
". . . nor shall private property be taken for public use, without just compensation."
In the Piscataway case, nobody is claiming that the municipality is taking the property without compensating the owner -- the issue is only whether the compensation is "just" or not.
To sum it up, folks: The Fifth Amendment of the U.S. Constitution clearly allows for the taking of private property for public use, provided the owner is adequately compensated.
However this is New Jersey and thier state constitution will rule the day.
I am a county official here in California and under Cal Enviro Qualitiy Act(CEQA) a conversion of farmland would require a full environmental impact report. That would at least tie things up for a year.
Under NEPA (national epa) the same standards are required as farmland is considered an important resource.
The law still stinks, but at least we could turn it back against the enviros.
Besides we just had a sale this week of some farmlands that went for $385,000/acre for about 80 acres of vineyard in NAPA.($31mill+/-) I figure the place in NJ is worth about $10 mill.