Laumont is very good (and I'd actually trust their desire to do the scan themselves), but imo there are other labs worth opening a dialogue with.

Did you talk to Griffin editions? They're good. And better still, they can print that optically for you if you wanted.

http://griffineditions.com/

BTW, if you've a chance drop by the Sugimoto show at Pace gallery (25th st) in Chelsea. Big fiber silver prints mounted on dibond with no face. Easily twice the dimensions your talking, which really aren't all that big, and I believe optically printed. But it's Sugimoto after all, so you can imagine how perfect they are.