The idea behind Jade Helm is primarily a psy-ops to get people used to seeing the military and their equipment in civilian areas. It’s the old Fabian tactics, slowly boiling the frog.
The second purpose is to regularize relations between military and local & state police & local governments. The military will also need to know where they will find resistance and where there will be support. Think of this as recon in “mastering the human domain”
Another goal for participants is “blending in” with the local population. This will allow the military to acquire information and test and refine infiltration and intelligence gathering techniques against suspected resistors (constitutionalists, Bible based Christians, vets, gun owners)
Drill for opposition crowd control and dissident extraction has already been documented.
This drill is expensive and has the potential to result in negative and possibly dangerous interactions with the public. It is the end of posse comitatis and Ted Cruz is right to be concerned.
There is at least one report from a Texas Ranger who saw trains that have shackles in them.