From Playbill.com:
According to press notes, "La Mirada Theatre will be completely transformed into Ewen High School, putting audiences, for the first time ever, at the center of the action in this bold and thrilling twist on the now-classic musical."
Two-time Tony Award-winning Broadway producers Bruce Robert Harris and Jack W. Batman (Pippin, Clybourne Park, On The Town) are working closely with Brian Kite, La Mirada Theatre for the Performing Arts and the creative team on this developmental production, aimed for major productions around the country.
Producers Bruce Robert Harris and Jack W. Batman added, "The story of Carrie has endured in the popular consciousness for decades, but no one has ever experienced it from this point of view. The idea of placing the audience in the center of this world was just too tantalizing to resist. We are working closely with the creative team to present an exciting new production of this reimagined, environmental/immersive staging of Carrie the Musical. If all goes well at La Mirada, we are planning future productions for cities around the world, probably kicking off with Las Vegas, New Orleans and Toronto. It's going to be a thrilling ride."
http://www.playbill.com/news/article/immersive-carrie-will-put-audiences-at-the-center-of-high-school-complete-casting-announced-for-l.a.-premiere-341325 It sounds to me like the immersive aspect is just the set. Perhaps the kind of immersiveness that characterized the CATS musical set?