"Eh? *scratches head* I'd really like more information on how they plan to do this...."
They will probably approach the people who have the rights and try to get them to sign them over under a new ePublishing contract. Then the publisher will OCR the text, edit for OCR errors, make a cover, format for Kindle, and collect royalties forever. The most interesting part will be the split of revenue between the publisher and rights holder.
Some rights holders will sign. Others will pay someone else a lump sum and collect all the royalties themselves. Others will do nothing.