@NS1, -This is a bit lengthy, but bear with me.
We can definitely appreciate your perspective, especially since the "railwatch for sand trains" has been going on since 2006, but I would have to differ with you on one thing. We are well familiar with the"shyster" you reference. He tried to interact in Somerville as well as out in Jersey City area and I believe his biggest play was outside of Baltimore. But he is not involved here.
Unfortunately, I fear you err in regards to the Clayton sand pit in Woodmansie. The sand pit itself and the 13 miles of track have been owned by the Clayton corporation since sometime in the early 1980's after the Jersey Central was absorbed by Conrail and the NJDOT took ownership of the entire ROW south of Lakehurst. Clayton purchased the ROW from NJDOT and ran his own trains utilizing Ashland Rwy until track conditions go so bad, it became too costly to operate. Clayton continued to pay the taxes on the ROW, although overgrown at that time until 2006 when Clayton had the line cleared (presumably in advance of looking for contracts for the intended construction of the new train tunnels under the hudson -"Tunnel to Nowhere" or The Macy's Basement Line. The project never came to fruition at that time (as a taxpayer, it was a very bad deal for NJ). At last look, NJ Seashore lines holds the contract to be the actual railway operator to transfer the sand cars to Lakehurst for conrail to take north. The "Shyster" has never been involved in any of this. As you said, his M.O. was to take abandoned ROWs and file to be recognized as an Operating Railroad. Never happened here.
It does appear that Amtrak indeed desires to conduct several projects (new tunnels, new Portal Bridge, and a few others). These projects may not show up for another 4+years, but there is potential for Clayton with this.
You are probably also very correct when you say "One carload of sand would have enough sand for at least 10 truckloads of concrete". As you are probably aware, a concrete truck hauls about 10 cy of concrete. 10 trucks would be 100 cy. 100 cy is paltry in these type of projects. Concrete would typically be measured in thousands of cy. And yes, like you said, they would also need the aggregate to go with it along with the concrete powder (would probably be a different vendor).
As far as locations for batch plants, Nj doesn't lack empty properties in the vicinity of the Hudson or Passaic Rivers where factories once stood, many of them having had rail access at one time. Not usually too hard to rent a property and set up a batch plant and reinstall a siding for unloading.
As far as when would this happen, you are again correct to be dubious as to occuring in the immediate near future. And as I pointed out in another post, Clayton would have to be contracted to be a sand provider, meaning his price and service would have to be lower than other sand vendors in a competitive bid.