Nothing big here, but if one of your capitol cities completes the invasion event and another doesn't, you can still *get* queued for the failed city's bosses.
Explanation: Early in the day when there's not as many people around, on our server Ironforge was cleared out and the bosses became available (Flamelash/Theradras). Stormwind however, failed to complete it in time and the bosses weren't available. 2 of us queued for Flamelash, killed him, and the group wanted to do the other bosses. The leader queuing was from another server that *did* complete both city events, so he queue'd and we were able to kill all 4 bosses, even though we couldn't directly queue for 2 of them from our server.
Steps:
1) Your server completes the invasion event for one capitol city, but fails the other one.
2) Queue for whatever boss is available, kill that boss.
3) Ask/Convince/Beg one of the LFD people from another server to queue/do the bosses that aren't available on your server.
4) Kill all 4 bosses... Profit, etcetc.
As said, mostly useless, but some may be able to make use of it.