Both the femtocell technology and the concept of mobile virtual network operators (MVNO) are believed to be key directions for future mobile network evolutions. This paper proposes a detailed model for the femtocell-based MVNO and analyzes the dynamics between the femto base station transmit power and its absorbing effect on the macrocell users via game theoretic techniques. The results show that the power settings given by the Nash equilibrium maintain the required QoS level without causing excessive interferences. Such numerical results should help the feasibility of large-scale deployment of femtocell-based MVNOs.