Not a VSP, but the answer is no.  When vehicle tags are run and the system is set up properly, then the vehicle identification info is returned and the DL information of the owner (or both registered owners) comes back.  Then if there are any warrants or CHP will be given.  Most MDT (mobile data terminals) will not be able to run that kind of information anyway (I am sure there are ways around it).  If the LEO wants to run a SN off a firearm they can, but it does not say what they have.  It will only say if the firearm has been reported as stolen.

If there is a 911 call at your home the county dispatcher and responding cops will be aware of any machine guns being registered.

VSP notifies the local agency that you are a registered machine gun owner. It is then up to that agency to do with the info as they wish. Some stick it in a file in a desk some where. Some enter the address into their data base so when emergency responders go to your house, you pop up on their computer as having a machine gun.  

In theory, that agency could set up their data base to be crossed checked when somebody in that agency runs your tag. I am not familiar with anybody doing do so.

This would likely be entered (if at all) as a premise hazard on a specific address.

He was talking about running plates, not necessarily whether they keep a database on file.  Most VSP run their tags from their vehicle.  This is not connected to local databases.

This is not accurate.

Some localities as mentioned above will do this, some will not.  Spreading rumour and false information like this without knowledge of the system isn't a great idea.

This is one more reason why the Virginia Uniform Machine Gun Act should be repealed. There's no reason for redundant state registration when the feds have it covered.