Comment 39 for bug 550288

Here is how it works for me now:

/lib/udev/rules.d/70-hid2hci.rules:
  KERNEL=="hidraw*|hiddev*", ATTRS{idVendor}=="046d", ATTRS{idProduct}=="c70[345abce]|c71[34bc]", \
    RUN+="hid2hci --method=logitech-hid --devpath=%p"

Bluetooth works, Mouse and keyboard work via bluetooth only. Pressing
the connect button on the Logitech receiver does nothing. lsubs output:
  ID 046d:c707 Logitech, Inc. Bluetooth wireless hub
  ID 046d:c703 Logitech, Inc. Elite Keyboard Y-RP20 + Mouse MX900 (Bluetooth)

Now I diconnect and reconnect the Logitech USB receiver. Bluetooth no longer
work, but the connect button on the receiver works and allows pairing
mouse/keyboard. lsubs output:
  ID 046d:c703 Logitech, Inc. Elite Keyboard Y-RP20 + Mouse MX900 (Bluetooth)

Actually, I can live with this and I can manually swtich between the two configuration.
But it's still not what was working in karmic with a USB BT receiver and keyboard/mouse
working vie Logitech proprietary wireless interface.