These modems would often slot into a Mini PCI-e slot in the netbook motherboard. [delokaver] figured out how to use these 3G cards over USB instead. It’s actually a fairly straightforward hack.
This showed that the Raspberry Pi would happily talk with a VL805-based USB 3.0 PCIe expansion card, as well as a Realtek RTL8111-based Ethernet card, but not a number of other PCIe cards.