for sure if the network does not start the ciphering procedure at all, you have a relief of your signaling load, of course.
But if you apply the ciphering procedure with value=”no_ciphering”, the only difference is that you have no ciphering on the radio inreface.
In fact the ciphering is applied by MS and BTS.
And the ciphering algorithms are quite simple ususally.
So there is a little effort and for MS and BTS only in this second case.
Ciphering procedure is done during the SDCCH phase, meaning that the MSC and the MS agrees on a certain ciphering algorithm. When you say “no ciphering”, it actually means that the A5/0 is going to be used.
The amount of messages on the SDCCH phase is the same, whether you use a5/0 or a5/1.
As said by Fedem, the ciphering itself is applied locally by the BTS and the MS, with no (or little?) effort from processors.