Power-law ensembles: fluctuations of volume or temperature ?

We present two issues here: (i) that in situation when total energy is kept constant recently proposed fluctuations of volume ensemble is equivalent to the approach using Tsallis statistics with fluctuating temperature and (ii) that the later (in which fluctuations are described by the nonextensivity parameter q) leads to the observed experimentally sum rule connecting fluctuations of different physical observables.