The theater where I was working 6 months ago had 1 NEC 2K projector and 13 Sony SRX R320 4K projectors. The Sony's were all installed after the NEC and we were told that Regal Cinemas had signed a deal with Sony for the projectors and Theatre Management Systems that they came with. It is highly likely that many of Regal's theaters are using the Sony SRX R320 projectors, however, some of the theaters that had earlier digital conversions may be using Christie or NEC projectors. You could always ask at your local cinema to see if they'd know (I'd stick to asking a manager, but even then, they might not have a clue). That's just my advice.
Former 35mm and Digital Projectionist @ Regal Cinemas
Currently watching on: BenQ W1070, 82" 1.0 Gain Screen, Darbee Darblet, PS3, with Yamaha RX-V473, SVS PB-1000, a Def Tech CS-8040HD, 2 SM65 for L/R, and 2 PM 800s for surrounds.