Could you link your official source? I am considering getting one so I don't have to drop a bunch of gold for a sandstone drake. But if they are not account level then i most likely won't get one.
Oh and to stay on topic, faction mounts turn into the other faction mounts when you faction change, so I'd guess it will work the same with account mounts.
EDIT:
Nevermind found them myself.
Originally Posted by Mumper
We have been discussing this issue the last couple of days and we made the call to make the following mounts account-wide:
Traveler's Tundra Mammoth
Grand Expedition Yak
Mechano-Hog
Mekgineer's Chopper
Sandstone Drake
Grand Ice Mammoth
Ice Mammoth
Jeweled Onyx Panther (all color variants)
Cloud Serpents (all color variants)
At this point, the only mounts that are not account-wide are either class specific or rewarded from PVP. We feel like both these types of mounts should still be character specific.
Thanks for your feedback on this issue!
Originally Posted by Vrakthris
No, the rewards from the Recruit a Friend promotion are specific to the character that receives it. We have received word that the current plan is that these mounts will remain specific to a character and not be made account wide.
Originally Posted by Vrakthris
Though it doesn't say "At this time" it does say "At this point" which can be an equivalent. As in, "At this point in development we're thinking that it should work like X". Feedback is still important though.
As always it is best to provide any feedback you may have for Mists of Pandaria content in the relevant areas. Mists of Pandaria is still very much under construction and very few things are written in stone.
So no they are not account wide, not or apparently in mists.