Yes, it is possible as per theory and as per my understanding of specification. Interface S8 is used between PGW (at home network) and SGW (at the visited network) to exchange the signalling messages and data.
When an UE attaches to the network PGW assigns the IP address. During the handover procedure, PGW does not change but MME and SGW can change. It means due to mobility UE can moves from source eNodeB to target eNodeB and in this case target eNodeB can be from home network as well as visited network. It is all about the agreement between two operators. If operator gets changed it means SGW will be changed and PGW will receive modify bearer request for the new SGW so that direction of data can change from PGW to new SGW
I have no idea on deployment whether such type of network is deployed or only at the lab level.
