Telekom Germany decided to give everyone who cares a free SIM with 2 x 5GB of LTE traffic at maximum speed. I am using it with the T-Mobile Speedstick LTE II on Ubuntu 14.10.
The device is recognized by usb_modeswitch and NetworkManager/ModemManager as shipped with Ubuntu 14.10, but usb_modeswitch would fail about 19 out of 20 tries, especially when connecting the stick to an USB 3.0 port. I changed the following value in
and rebooted the installation. Now usb_modeswitch seems to be able to reliably switch the device.