At the moment this is done through metadata that is updated by the server, this does however mean that all states inbetween those syncs (e.g. tick counts) are not updated at the client side. By making use of NBT (which is synced when a TileEntity is created, due to the code in EvilCraftTileEntity) and letting the client emulate the server's code this can be solved.
This will be particulary useful for bad weather effects that require special rendering on the server side and change when the number of remaining ticks decreases.

I've already (partially) implemented this in 8398801 by also ticking on client side.