[MilCom] ARNG Aero Railroad Track Surveillance & Security Mission?

[Ken]

Today at work (approx 1445 hrs local), I heard & than observed 2 UH60 helos 
flying at about 400 to 500 feet flying above the CSX railroad main tracks in 
Palmer MA.  Was out of my office in a different part of the building, so 
didn't have my scanner with me.  When I got back to the office, turned the 
scanner on but didn't monitoring any air/air comms or ATC comms.   Wondering 
if anyone else has obserfved military helos flying at relatively low 
altitudes following railroad tracks?   Perhaps this is another "homeland 
security" type mission that ARNG Aero assets are practicing for?

Ken
Springfield MA Monitoring Area