You can use multiple powerline controllers at the same time. The ISY supports either the 2412S Serial PLM or 2413S Dual Band Serial PLM. I think you would have to limit a given Insteon device to one or the other. Trying to manage and control the same device from two different systems could be a logical issue. I am still monitoring for Broadcast messages from the EZIO6I. Sunset is a few hours away. No Broadcast messages since mid morning when I lowered the AN1 analog trip points to get AN1 to show an On state.
The 2413S Dual Band PLM does not provide 12V power as the 2412S does so an external power supply (wall wort) is needed if using the 2413S.