As you can see he has an icy aura eminating from his front feet.
This is an appearance-only effect, not a buff. This means he is completely safe to trick-tame BUT will lose the ice if he dies etc.
METHOD: The first time I attempted to trick-tame him right off the bat, waiting until I had 2 seconds left on the tame before spamming the petabandon macro then immediately relogged. This attempt, however, failed. The second time I tried taming something first then trick-taming Icehorn. He was down at the ocean for this one with nothing tameable close by so I tamed a condor from a way off and came back. I don't know if time is an issue or if I simply got unlucky but again it failed.
This last time he was at his north-eastern spot within taming distance of some condors if I stood between them. I grabbed one of the birds and dismissed, then attempted the trick-tame immediately. Relog: success! The rhino was standing proudly at Varethyn's shoulder.
It took me a little over a week to get this right, having only seen him 3 times.
Tip: Do everything you can to increase framerate (low graphics settings) and reduce MS (turn off addons) for a higher chance the macro will take effect at the right time.
He's certainly been a hit with the guild so far. All I need now is a name.
I appreciate all the names of course but I also made a thread over in Name That Pet 
*ponders*
However I never camped for him, only flybys just to see if it was possible.
