Ohh - I have mine going but haven't installed the SDK yet, so I'll do you a trade.. :-)
As with any USB device, they have a VID (Vendor ID) and PID (Product ID). The linux device will see the VID and PID but you will have to tell it what hardware this is.. Is it a keyboard? Mouse? How can it communicate with the Cellphone modem? Looking at the docs for the UBlox Sara-201, it says that it has a few connections but one of them is an AT command set interface. Historically (if you are old enough to remember the 9600 baud modems we used to access the internet with in the early 90's...) modems with an AT command set are based on serial links. So in this case I took a guess and just said that the device is a serial device.
To get the PID and VID, you need to do the following:
Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 001 Device 003: ID 1546:1102 U-Blox AG
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
So, device 3 is the U-Blox cell phone module. The ID 1546:1102 id the VID and PID. CD to /etc/modules.d and edit the file usb-serial with the contents, "usbserial vendor=0x1546 product=0x1102 maxSize=2048"
This includes the VID and PID from the command, "lsusb" above and tells the omega that there is a serial port.
root@Omega-F5C5:/etc/modules.d# cd /etc/modules.d
root@Omega-F5C5:/etc/modules.d# cat usb-serial
usbserial vendor=0x1546 product=0x1102 maxSize=2048
Install screen with opkg install screen
then cd to the /dev directory and ttyACM1 should be there
pipe the port to screen
screen ttyACM1 <enter>
and then you are connected to the modem. Try AT <enter> and it should say OK.