This is straight from the mouths of the Lowry guys:

"We were working at 1920 by 1080 at full RGB." So that throws out the 4K theory. I remember asking at least twice in the same thread what resolution the Indy trilogy was restored at and no one answered my question. I'd thought I read somewhere that it was 4K, but if one of you guys knows then please clarify 'cause I'd like to know.

-lossless compression or none at all: probably true

-saving the cgi files: I've been curious about this for a while. When I first watched the '04 dvd's, it looked to me like the '97 cgi shots had simply been scanned from the negative just like everything else. I only say that because I thought I noticed a very, very slight flicker and/or framedrift in shots such as the asp knocking the floating droid to the ground right before Luke's speeder zooms into frame. The shot of the Falcon about to touch down on the Cloud City landing pad (right before it cuts to the miniature) is another example. Then of couse there's also the example of the color that got sucked out of a '97 shot during the battle of yavin (when wedge flies through the exploding tie fighter he shot). So I don't know if he saved the files.

-saving all the old VFX elements: they're right about that. Any making-of on the SE will mention this.