It can definitely be different because most mobile operators have a different back end rather than simple IP based devices.
For e.g. on my network we have shared IP addresses and incoming connections are blocked.
Also, mobile operators can modifiy the packets as they go through, especially for bandwidth conservation they can set the user agent to 'mobile device' or something like that.
If you are lucky to have your own server, you can test this.
Btw...bad request means that the request isnt even going out? Is this the response from the server?