Mobile Internet ( WWAN ) for thinkpad x200s with Linux. Ericsson F3507G.
I was able to install a mobile internet mini-PCI card in a thinkpad x200s, compatible with Linux Mint 13 ( or Ubuntu 12.04 LTS ).
I bought an Ericsson F3507G mini-PCI card on Ebay, making sure that the part number is compatible with this thinkpad. The thinkpad BIOS has a "whitelist" of permitted card models, so it's necessary to check compatibility.
I followed the hardware maintenance manual to find out how to remove the keyboard and he palmrest. Under the palmrest is a socket for the card, and an antenna connector. I plugged in the card, attached the antenna and screwed it into place.
I looked in the network manager after booting the machine and couldn't see the card, nor was there anything in "lsusb" and "lspci". So I rebooted, and set the BIOS security setting for blocking WWAN cards. Then I rebooted again and unblocked the security setting. This time the card was found in network manager. I'm using a Tesco Mobile SIM, so I used the network manager wizard to set up a connection using the Tesco APN.
The card seems to use about the same amount of power as wireless LAN, according to powerTOP, ( about 1 watt when surfing, and 20 mW when idle ), so it's useful for working on battery power.