Yes. You need the file to be hosted on a workstation with a fixed IP inside your network. On your router you need to forward traffic on port 5003 to that IP address.
On the FMGo devices (or any device running FM Client) set up a Favourite by using 'Open Remote' and direct it to the Public IP address of your router. The device will then see the hosted file and can open it as normal.
Note that you need to know your public IP, and if you have not been allocated a static IP it will change periodically and then the remote users will not be able to connect without being told what the new IP address is. The way around that is to either pay for a static IP address, or use a service such as DynDNS or No-IP .
FileMaker iOS Development Kit
Filemaker Go for iPad and iPhone
Filemaker Go Help for iPhone
PDF - Filemaker Go Development Guide