Stock DIGI net mobil USB dongles, 21.6 Mbps, distributed by RCS-RDS Romania http://www.rcs-rds.ro to its residential clients (BLUE modem). At the time of the test (April 29th, 2014), it probably doesn't work just because is „seen” as a mass storage device, not USB modem (in usb_modeswitch).

lsusb

Bus 001 Device 003: ID 19d2:1514 ZTE WCDMA Technologies MSM

lsusb -v

Bus 001 Device 003: ID 19d2:1514 ZTE WCDMA Technologies MSM 
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               2.00
  bDeviceClass            0 (Defined at Interface level)
  bDeviceSubClass         0 
  bDeviceProtocol         0 
  bMaxPacketSize0        64
  idVendor           0x19d2 ZTE WCDMA Technologies MSM
  idProduct          0x1514 
  bcdDevice            0.01
  iManufacturer           2 ZTE
  iProduct                1 MF195E
  iSerial                 3 AF7C136E43254C7846BA6FD2952C656312144268
  bNumConfigurations      1
  Configuration Descriptor:
    bLength                 9
    bDescriptorType         2
    wTotalLength           32
    bNumInterfaces          1
    bConfigurationValue     1
    iConfiguration          0 
    bmAttributes         0x80
      (Bus Powered)
    MaxPower              500mA
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        0
      bAlternateSetting       0
      bNumEndpoints           2
      bInterfaceClass         8 Mass Storage
      bInterfaceSubClass      6 SCSI
      bInterfaceProtocol     80 Bulk-Only
      iInterface              0 
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x01  EP 1 OUT
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0200  1x 512 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x81  EP 1 IN
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0200  1x 512 bytes
        bInterval               0
Device Qualifier (for other device speed):
  bLength                10
  bDescriptorType         6
  bcdUSB               2.00
  bDeviceClass            0 (Defined at Interface level)
  bDeviceSubClass         0 
  bDeviceProtocol         0 
  bMaxPacketSize0        64
  bNumConfigurations      1
Device Status:     0x0000
  (Bus Powered)

dmesg

[  921.920022] usb 1-5: new high-speed USB device number 6 using ehci_hcd
[  922.064968] scsi10 : usb-storage 1-5:1.0
[  923.066257] scsi 10:0:0:0: CD-ROM            ZTE      USB SCSI CD-ROM  0001 PQ: 0 ANSI: 0
[  923.066744] scsi 10:0:0:1: Direct-Access     ZTE      ZTE Storage      0001 PQ: 0 ANSI: 0[  921.920022] usb 1-5: new high-speed USB device number 6 using ehci_hcd
[  922.064968] scsi10 : usb-storage 1-5:1.0
[  923.066257] scsi 10:0:0:0: CD-ROM            ZTE      USB SCSI CD-ROM  0001 PQ: 0 ANSI: 0
[  923.066744] scsi 10:0:0:1: Direct-Access     ZTE      ZTE Storage      0001 PQ: 0 ANSI: 0
[  923.076127] sr0: scsi3-mmc drive: 0x/0x caddy
[  923.076406] sr 10:0:0:0: Attached scsi CD-ROM sr0
[  923.076651] sr 10:0:0:0: Attached scsi generic sg0 type 5
[  923.077134] sd 10:0:0:1: Attached scsi generic sg1 type 0
[  923.079014] sd 10:0:0:1: [sda] Attached SCSI removable disk
[  923.177530] sr0: CDROM (ioctl) error, command: Get event status notification 4a 01 00 00 10 00 00 00 08 00
[  923.177547] sr: Sense Key : Hardware Error [current] 
[  923.177552] sr: Add. Sense: No additional sense information
[  923.293526] sr0: CDROM (ioctl) error, command: Xpwrite, Read disk info 51 00 00 00 00 00 00 00 02 00
[  923.293543] sr: Sense Key : Hardware Error [current] 
[  923.293548] sr: Add. Sense: No additional sense information
[  923.554162] ISO 9660 Extensions: Microsoft Joliet Level 1
[  923.557179] ISOFS: changing to secondary root
[  923.076127] sr0: scsi3-mmc drive: 0x/0x caddy
[  923.076406] sr 10:0:0:0: Attached scsi CD-ROM sr0
[  923.076651] sr 10:0:0:0: Attached scsi generic sg0 type 5
[  923.077134] sd 10:0:0:1: Attached scsi generic sg1 type 0
[  923.079014] sd 10:0:0:1: [sda] Attached SCSI removable disk
[  923.177530] sr0: CDROM (ioctl) error, command: Get event status notification 4a 01 00 00 10 00 00 00 08 00
[  923.177547] sr: Sense Key : Hardware Error [current] 
[  923.177552] sr: Add. Sense: No additional sense information
[  923.293526] sr0: CDROM (ioctl) error, command: Xpwrite, Read disk info 51 00 00 00 00 00 00 00 02 00
[  923.293543] sr: Sense Key : Hardware Error [current] 
[  923.293548] sr: Add. Sense: No additional sense information
[  923.554162] ISO 9660 Extensions: Microsoft Joliet Level 1
[  923.557179] ISOFS: changing to secondary root