I happen to know that someone is working on a plugin for controlling recipes already. I think its very near to completion.
Yes; because I told him how. I'm reluctant to tell you until he's released his plugin though. Basically, the only way to do it is by interfacing with the minecraft server itself directly. There's no way to do it with the methods exposed by the bukkit API (yet)
Hehe who else would know how to communicate directly But that's a pretty dirty way to do it, not that it means it's unstable or anything, if done right.