I haven't had the chance yet to test all the variables such as locations, group types, and different buff types, but I CAN confirm that it seems to work in WSG.
Basically, after I gave the 30 min wisdom to priests and pallies, one of the other pallies decided to give everyone economy 10 min buffs of the same. Sure enough, at least me and the priest had 2 active blessings of wisdom. I am prot spec, so theres no wisdom enhancements on my end, I'm not sure about the other guy because he was on another server. I will screen shot later to demonstrate as soon as I get in a battleground where a different pally does Greater wis, so I can do a wimpy wis.
I haven't raided since the patch, so I can not confirm if this works in raids or PvE groups. Also, there's a -small- chance that it only works if someone from another server buffs it, again I haven't been able to test all the variables. The only reason I say this is because WoW seems to forget who gave you the buff when you move from one server to another (such as the have two auras exploit upon transfering).
I dunno... will post with updates.
If this proves to be the case, I suggest goign into AV, getting a million group buffs, use the quit battlground without the deserter flag trick, and requeue so that you're removed from that BG server (and thus wiping WoW's recollection of who gave you buffs clean "These are not the buffs you're looking for") and entering a different match for seconds helpings before the cooldown expires.
* thinks * I've nver seen 2 greater wisdoms on at once, but if it's an issue of cross server interaction and the like, what I said in the previous paragraph might enable staking of buffs. I don't know and I don't have to test now, but I certainly will this evening because I've intrigued myself.