Christensen and Lund (1999)1 (discuss the general architecture or algorithm structure of multi-channel room simulations deployed in a number of TC Electronics products. There seems to be at least some overlap with how Spat is working.
References
1 Knud Bank Christensen and Thomas Lund (1999): Room Simulation for Multichannel Film and Music. Presented at AES 107th Convention, New York, September 1999.