  In amorphous solids as in tissues, neighbor exchanges can relax local
stresses and allow the material to flow. In this paper, we use an anisotropic
vertex model to study T1 rearrangements in polygonal cellular networks. We
consider two different physical realizations of the active anisotropic
stresses: (i) anisotropic bond tension and (ii) anisotropic cell stress.
Interestingly, the two types of active stress lead to patterns of relative
orientation of T1 transitions and cell elongation that are different. Our work
suggests that these two realizations of anisotropic active stresses can be
observed \textit{in vivo}. We describe and explain these results through the
lens of a continuum description of the tissue as an anisotropic active
material. We furthermore discuss the energetics of the dynamic tissue and
express the energy balance in terms of internal elastic energy, mechanical
work, chemical work and heat. This allows us to define active T1 transitions
that can perform mechanical work while consuming chemical energy.
