Decrypting SSL over a Mobile Network

I work for a large company and we are trying to judge the safety of some proprietary information that is being sent and received in a new application we are developing.

After our initial testing we realized that we could easily do a MitM attack with Fiddler over wifi in no time in all - leaving a bunch of information in the open. Since then we changed it so that our company's proprietary information can't be sent over wifi but instead over network only.

So the question is, is it possible for someone to decrypt our https packets over the mobile network (QXDM Possibly)?

Understandably if they get our private keys they could do it with wireshark but we are going to assume that it wont be the case.

If you know of any methodologies - we would like to test them against our app.

Thanks You,