Sounds like they may use something similar to the pinball hardtop that OutsideEdge introduced at Expo in October.
https://pinside.com/pinball/forum/topic/hardtop-playfield-new-product-announcement-poll-included
http://www.pinballgifts.com/hardtop.html
Using something like that, as a customer, it would be relatively easy to retheme or develop your own game. Change out the overlay, software (or rule set), and plastic set. Might also explain multiple games being available at the same time.