MATLAB Mobile does not require that the cell phone be on the same local network as the PC. You can tell MATLAB Mobile to connect to a public IP address.
The rest is a matter of firewalls allowing the ports, and it might involve setting up static Network Address Translation for the port if the public IP address gets you to a router that is doing Network Address Translation for an internal LAN.
The main thing about MATLAB Mobile is that there is little to no security built in to the process -- no encryption of packets, little or no authentication that the incoming packets are from an authorized user.
I would thus recommend that you consider using a Virtual Private Network (VPN) between the phone and the PC.