Oh yeah,
that one. Intel couldn't be arsed to provide a Linux PCIe driver for that one.
Unfortunately, if you're betting on
the code by James Wah (abrasive), that won't get upstreamed anytime soon: it is based on the wrong paradigm ("just duplicate the effects of the Windows driver with minimum effort, hopefully someone else can clean it up later"). In particular, all the "RPC" stuff should be done by the kernel driver, preferably as ioctls on the data character device, with the best interface discussed with linux-netdev and ModemManager folks. There will eventually be other Cat9 WWAN devices with PCIe interfaces as USB2 480 Mbit/s is increasingly insufficient, so better try to get it right from the get go.
(Although AFAIK xmm7360 only reaches 450 Mbit/s down, 50 Mbit/s up, so the difference shouldn't be
that big between PCIe and USB.)
Is there a better variant of the kernel driver I don't know of? Hopefully..