Put it this way. They're building more cars right now to fill the EOQ rush, and most likely they'll have cars lined up and ready to ship out on trailers throughout the next few weeks.
During that time, you might get a "car spotter" driving by the area and snapping pictures of the new cars all lined up and ready to ship out to delivery centers. When they post up those pictures online, then it usually spreads throughout the community and you'll eventually see it. That'll show you just how busy they are and how many new cars they're pumping out.
That, or just keep an eye on inventory in different areas as new car builds get delivered over the next few weeks.