I'll tell ya what I know about WB ink & paint. During the years we serviced Warner Bros (1992-2000), it was understood that all shows were to be produced on 35 mm film. The explanation for this was that the industry was in a state of flux and they were looking forward to the Hi-Def Era, and knew that 35 mm film was the best medium for retaining the highest possible definition regardless of which way the tech geeks went. In this they showed a lot of foresight; other cartoons made in that era will not stand up to Hi-Def.
So we delivered everything on film according to their wishes. The only exception was on "Dot The Macadamia Nut" where we composited a few shots digitally: the ones where it shows all the characters in three vertical columns, like the slot machines (we even threw in some lemons, cherries, and bars to enhance the joke) (e.g. one such scene is at the 23-to-25-second mark of that cartoon) We then printed those digital files to film and delivered them with the rest of the shots.
Everything else for Warner Bros was done with xerox, cels, and film. We did have the ToonBoom Digital Ink & Paint System and used it for all our other (smaller) projects. The interesting thing was that ToonBoom uses a vector-based image software, so the files could've been submitted at Lo-Rez for the medium at the time, and then recomposited at Hi-Rez at a later date ... but WB wouldn't budge on that issue.
