Well as far as the cheap part goes, my thinking was that these buildings definitely already have internet service in the first place, may as well just utilize that.. I supposed you make a point about reliability, but then again they're putting up with the whole 2-way radio interference, seems like the bar is already set low :P

I don't know, again I'm just thinking out loud, I'm no HVAC professional. We do use the internet to manage off site devices in my company and we tend to have more issues with power outages than we do with our ISP uptime, it's been a good solution for us.