How are you going to check? iOS is closed-source. You cannot monitor the traffic 24/7 over the whole lifetime of the device. Maybe the fingerprint delivery can be ordered remotely.
It's a phone... If you are concerned that your fingerprints MIGHT be uploaded you need to consider just not using a smartphone. AKA "a voluntary spy device".
It's quite odd. Here's a device that can listen to everything you say all day long, that can read all of your e-mail, take pictures of you and your surroundings, sniff all of your passwords, etc. etc. etc., but people are freaking out because it might be stealing your fingerprints, which you leave thousands of on various public surfaces every day anyway? I just don't get it.