Hi Takeshi - Under the same settings Patrick has indicated here, is content enabled or H239 enabled? If H239 enabled, this will disable BFCP, and it wont advertise it. Can you verify?
If enabled, then verify with a screen capture on the conference page the C-series sending content to the Jabber Ipad client, and lets see whats going on there? The screen capture or even the event log may give you a warning as to why it can't send it to the Ipad. This would be helpful.
Also, just to verify, there is no CUCM here or anything correct? Ipad is registered to VCS?