Without there being any mention of exactly how the service will interact with the phone it is hard to say for certain it will be Verizon only, but I assume it will. If Verizon is funding part of the project I can see them making it Verizon only. The article mentions an application that is loaded on the phone, but makes no mention of the hardware or OS requirements needed to run the application. If the application is not OS agnostic then not only could it be carrier limited, but all phones on the Verizon Network might even be supported.
Until the details of the application, if it really even is an application and not an SaaS implementation, are announced it is only a guess as to what carrier and phones will be supported.