As i recall #showtooltip works for macros which are dragged from the blizzard macro frame into infini bar slots, but not for embedded makros. I hope #show will do the trick, that would be great.
Edit just triied does not work. Here one example:
#show [stance:3,nocombat] Prowl; Catform /cancelform [combat][noform:3] /dismount [mounted] /cast [nostance,nomounted]Catform; /cast [stance:3] !Prowl /equip [nobutton:2] item:29390 /equip [button:2] item:33509
This works in the blizzard ui showing either Prown or catform. As an embedded macro in Infinibar it shows, if in Catform and already stealthed, the icon of item:29390. Disclaimer: Ability names might be a bit wrong as i am using the german client.