The link provided by Arthur confirms that the device in question actually is a "USB mobile modem." Calling it a "dongle" perverts the traditional meaning of the term, which has customarily meant a "hardware device with the exclusive purpose of preventing use (of software or associated hardware) on more than one computer at a time."

The proprietary features of this device, locking a particular modem to a single wireless service, vaguely support calling it a "copy protection" (DRM) device, so "dongle" is perhaps only a mild corruption of tradition. I haven't seen the term used in the US, although that's possibly a result of less universal availability of wireless (cell) connectivity here, and more careful avoidance by our wireless/cell phone providers of terms traditionally in disrepute.

To old-timers (here) with experience with a traditional "dongle," "here's your dongle" may evoke a reaction similar to "here's a nice gob of phlegm," or "here's a nice hairball the cat just spit up."

John