Inverters and solar battery storage generally have some combination of wired and wireless communication. You need to communicate with the grid for real-time pricing and forecasts so the system knows when to charge and discharge. Also you want the system status of all the panels and batteries. If somebody slices through the wrong fiber line near your site, it’s important to still be able to get that information.

If you get a home PV system, they’ll often have the option of a cellular modem. The controller on my home system has Wi-Fi and Ethernet with the option of a cellular modem. It wouldn’t surprise me if the board comes populated with some of the components necessary for cellular functionality even if you don’t opt for it.

I’m just saying they need to divulge more details before one can conclude this is nefarious.