When I restore a multisig wallet in Electrum 2.6.4, the dialog appropriately prompts me to put in the three xPub or seeds needed to view the funds in the multisig wallet. When I click Wallet->Master Public Keys, I can then review these 3 public keys which makeup the multisig wallet.

Obviously in this case Electrum has deterministically generated some addresses from this combination. How can I see or generate a single xPub key for the multi-sig wallet so I may view all the transactions in a wallet-watching service?