Buildcraft 2.2.1 is out for SMP!
This is how this will work:
I am setting up a second dedicated server to run our existing world on. It will be at play.inventioncraft.com:25550.
Please logon to it and gather your items into a safe (this is all items you want to take to the new world; machines, ores, cables, etc.) Please keep this limited to two safes, although if you have more, I can work with you on that. An admin will be coming around and verifying ownership of safes and then moving them to the new world (once it is set up).
It's going to take me some time to get the new world put together and everything set up, so bear with me for a little bit. For the time being, continue on play.inventioncraft.com.
I will post here as soon as I have an update.