from what i've read he was hired with the verbal promise that he'd be providing the transformation, put a lot of personal (unpaid) time into working out how to do it, and then at almost the very last minute they decided to go with cgi
here's a guy for which the special effects makeup artist academy award was created, i'd say it's a bit weaselly on the part of the producers
twist spoiler:
spoiler (click to show/hide)
his dad is the original "evil" wolfman, and you'll get to see seventy-year-old anthony hopkins turn into a wolf and scrap with benicio
:lol