According to news reported by Bloody Elbow Diarist "mixer", this fight is likely not happening:
Tatame magazine just published a brief interview with Ricardo Arona where he denies having signed with M-1.
He says that he had heard rumors on the Interned, about him allegedly signing with M-1 but never actually received an offer from them. In fact he claims to have never even heard of the event.
My guess is that Fedor's first fight is either with Mark Hunt, Josh Barnett, or a total scrub. They either want to start Fedor's association with M-1 off with a bang by having him fight legitimate talent or they want to showcase their marquee star.