(You know, the usual I-did-a-search-and-found-nothing, except one thread which was about Spellsteal - this one is NOT.)
This is how I got 2 of my own armor buffs on my Mage at the same time. I'll get over this as quick I can:
1. I buffed up with X Armor.
2. Transfered my Mage to another server.
3. Logged in on my Mage on the new server and used Y Armor.
In my case I used Molten Armor first, and then Mage Armor after the transfer, but in theory all 3 (4?) would work this way.
Also, a screenshot: (fix the link yourself, I'm just a pretty leecher) wowbucket.com/uploads/1233032935.png