Mounting worked last time I tried, but I used ress/kill instead.
This is an old macro I had on another shard for mount/dismount tame. It might not be super stable though in case you anger your pet or something, fyi. Heavenly ostards cannot be angered afaik.
https://drive.google.com/open?id=0B5x_NQz3CXmXSjd4dFZCNEstb00
lonewolf
