Q. If I have multiple ExpressRoute circuits in different regions if one is Premium can all contact all regions?
A. ExpressRoute Standard provides connectivity from a corporations on-premises location to all Azure regions in that geography but not Azure regions in other geographies. The ExpressRoute Premium add-on extends the connectivity to all Azure regions throughout the world using the Microsoft backbone but only for that ExpressRoute circuit. This means the geography with the ExpressRoute Premium circuit will be able to contact all Azure regions through the globe however the other geographies with ExpressRoute standard circuits will only be able to access Azure regions within their geography. If you need all locations to access all Azure regions globally then all locations need ExpressRoute Premium.