The proposal you linked would not work if the specific USB interface was set up correctly to only allow a specific device (identified by a specific whitelisted

The proposal you linked would not work if the specific USB interface was set up correctly to only allow a specific device (identified by a specific whitelisted USB device descriptor) to operate only with a specific driver. This internal USB interface in the Neo900 will allow this sort of configuration which would prevent the attack you suggest. Sure if you plug in random USB devices via the OTG port or the pins under the battery you could attempt this attack (if security was once again loose on those ports) but hopefully your USB keyboard/mouse/flash drive or whatever you're plugging into there is less dangerous and black-box than a baseband modem. And heck, if you are still worried nothing stops you from applying the same security measures to those interfaces as well.