I was refering to this collection http://www.amazon.fr/Lint%C3%A9grale...eywords=uderzo, with volume two out this month.
From Gaston #8 it is indeed a coloured scan process for the original pages (it's the same for Spirou starting with QRN). In french it's referred as "fac similés". Like the Hellboy IDW AE, if the original pages are untraceable, they used plain B&W reproduction from the films. For Franquin it's a long process to gather these pages and they only publish a volume once a year in the best of cases. For Uderzo I have seen somewhere that he has kept all of his original work (but all the pages from one of the asterix album has been stolen), so it will be easier to publish this material, although this treasure hasn't been exploited yet.