Enabling the Internet to Vehicular multicast communication is fraught with challenges due to the heterogeneous nature of the two networks. We study the robustness of the multicast routing structure in vehicular networks for data flow from the Internet to a set of vehicles. In this paper, we investigate the impact of urban traffic dynamics on the link stability of the multicast tree. Our study shows that in an intersection scenario, the link can be sufficiently stable without depending much on the relative direction of the vehicles, while on straight roads, the link stability is largely affected by the relative direction.