Apparatus, and an associated method, for facilitating routing of packet-formatted data in a packet radio communication system. When a mobile node roams out of its home network and into a foreign network, data routing is facilitated. A UPA (unique private address) tunnel, is selectably formed between the mobile node and a foreign agent. And, a UDP/MIP (User Datagram Protocol/Mobile IP) tunnel is selectably formed between the foreign agent and a home agent. Problems otherwise associated with the private address conflict and NAT/NAPT device traversal are avoided.