Update: I got an email from the Roadmaster design shop in Vancouver, WA a couple days ago. One of the design engineers looked at an Energi and confirmed the brackets for the hybrid work for the plug-in hybrid too. So, they already have the brackets for both Cmaxes.
Anyone towing a plug-in hybrid yet? I've ordered a Cmax Energi and am waiting for Roadmaster to do the engineering. They've asked for one to do that. Hope mine gets here so I can offer mine since I live just 50 miles from their engkneering staff and would love free brackets.