FDNY SOC company’s have them in addition to the gas powered saws , not as a replacement. The battery power saws don’t have the power or tourque of the gas powered saws .there intent is be used in confined spaces ,like in building collapse , subways ,or ant place where gas fumes can become a issue . The are also excellent for restaurant fire when the fire is in the duct work. The light weight saw makes cutting the over head duct much easier, safer and faster . Also not uncommon to find security roll downs in the stairways or on interiors doors on commercial or loft type buildings.
They have there place , but not to replace the gas powered saws. A 9” blade really isn't deep enough for roof Opps.