I think it happened when I broke the pipe (Builcraft stone transport pipe), which was actively used for power (MJ one) transit at the moment...
http://pastebin.com/nFHB6za7
Last line repeated for a while, server hangs so no complete crash log. Also the server log was a complete mess.
I know about the Cauldron server that I'm using. If this bug is somehow related to it, I will try to reproduce this bug on a vanilla Forge server later. But I think I also had that bug (or similar) in a singleplayer a few days ago...

Tried to reproduce the crash (still no vanilla yet): yes, it happens when I broke a pipe. It didn't happened at the first try, though. Also in both crashes I've found this: http://pastebin.com/1EKq5i5M, last line kept growing. Don't know what it means and even was not sure if it from Logistics Pipes at the first time, but it appeared in the both crashes (and only in these), so I assume it is related.