The production is delivered to the theatre on a hard drive for display. If the production is very short, it can be delivered on a thumb drive.
I found a FREEWARE application called DVD-O-Matic which has allowed me to create a DCP and have had it projected on a 35' movie screen in a "FLAT" 1.85:1 format.
The video quality was the same as viewing it on a HDTV.
This opens up a whole new avenue for those wishing to publicly exhibit their work on something larger than a flat screen tv.
My workflow was full HD camera/PD11/Produce (custom profile) h.264AVC/1920X1080/24P/high profile/cabac/avg25000kbps/dolby 5.1/384kbps. The target directory, for the production I called "Productions". It can be any folder that you wish to create.
Most film festival entries that are selected for finalist screening, must be be submitted in a HDCAM tape or DCP format, some accept blue ray dvd's for selected screenings.
Cheers, Jerry