Hi Adriaan,
Yes, you can have simultaneous TCP socket and GPS.
The MTSCellularInterface code can be found here:
https://github.com/MultiTechSystems/MTSCellularInterface
It implements sockets in command mode allowing GPS while TCP sockets are established. You can find a couple examples of MTSCellularInterface in use here:
https://os.mbed.com/teams/MultiTech/code/Dragonfly-Examples/wiki/Homepage
Kind regards,
Leon