Surely they're not surprised that the Islamic service would include "Allahu Akbar". It's as much a part of that service as "Amen" is in a Christian service.
The real question is why in Heaven's name would they want an Islamic service in a 9/11 memorial ceremony at all. There should be limits to tolerance when it gets in the face of those we are memorializing.
Does it not seem odd to have an interfaith service at a Catholic university anyway?