My utility is on there, but no way in hell am I allowing them to control my thermostat, which is a requirement of this program. There is a catch to "free".
Some may not mind that requirement though.
In my opinion it is a precursor for the utilities to charge a premium for excessive use. I see it happening in the healthcare industry. My last workplace offered a discount to those folks who agreed to have a number of health tests (bloodwork, hypertension, obesity, smoking etc) performed.
If you were "healthy" or you agreed to participate in whatever program in needed to address your issue you would be given a discount. Sounds good and perhaps it motivated some individuals to become more healthy. However I could also view it as a mechanism to up charging those who are not healthy. One could see this direction is dangerous in the long run.
ECO+ mode was the first "voluntary" setting, where not only your humidity and temperature is accounted for but also signals from your electric company. I have since turned off ECO+ in all my Ecobee's and recommended it to be off to others were we have installed the thermostats.
Sounds like you could have the utility company controlling your thermostat AND Ecobee's routine server outage where you also lose control. Pretty sure even if they paid me monthly I wouldn't take this deal.
Actually you can never lose control, the periods of control have limited time duration and the thermostat in offline mode will return to normal operations. When I found out that ComEd here in the Chicago was in the program I read up on what they are allowed to do.