The 2015 published Cochrane review (1) found only five studies that evaluated community walking sessions for people living a stroke. And, they concluded that the quality of evidence of these studies was very low. Furthermore, only 266 individuals had been involved in all five studies and two of the programs “mimicked” community programs.
Walking certainly improves walking ability and speed after a stroke event; the activity itself brings a multitude of benefits not only economically but socially also.
I could not find any reviews published after 2015.